WIFI Calling Preferences Being Forced to Cellular Preferred

Having an E911 address set in the first place is the first essential part for Voice over LTE, video calling, and WiFi calling features to become active and usable at all in the first place, otherwise yours was functionally disabled without it, even though the toggle is there, with no E911 it causes IMS registration to fail, dis-allowing these functions entirely from the cell tower on device bootup. Testing with Airplane mode on then wifi, calls will drop regardless if E911 address is not in place, IMS Registration status is verified in SIM card status will tell you if Voice over LTE, video calling, and WiFi calling features are active and functioning Now that you have it, it WILL be a matter of time until you find this setting changing to cellular preferred constantly occurring throughout use as most ALL other carriers included Android 9+ Google software bundled phones go. Tracing through logs in App Ops I have identified this change over issue down to a combination of all softwares, implemented first by Google through most any Play Store apps eventually brought into standard Android OS development and also infused into vendor/carrier installed apps just the same is the ongoingly largest battery draining issue - randomly occurring wifi scanning also mixed in with Geo Location/NFC triggers which are all binded directly with GPS Location Services function. Bottom line primary trigger causing "Cellular Preferred" changes is limited consistent Wi-Fi internet data throughput or bandwidth, this by absolutely no means is wifi signal strength at the router but combination of all specifically between the modem itself and the wifi calling app itself on your device, home modem internet signals are rarely consistent although your wifi might be bad ass at hiding it for other types of devices; this can all drastically be affected also by excessive Google/games/apps limiting bandwidth to wifi calling app also multiplying the issue also having wifi scanning built into everything.  Wifi scanning basically momentarily pauses or severely limits your current wifi connection while the radio adjusts between wifi channels trying to locate other networks to meter yours against, causing the wifi calling app to disconnect unexpectedly and flip to cellular. This in turn blows for us all because it is implemented into almost all newly developed/updated apps to be allowed in the Google Play Store, even the built in Android app that senses input from a simple touch of your touch screen and keyboard apps cause wifi scanning to momentarily take place, had mine changing it seemed 50% of the time swiping my screen to unlock. The standard Android settings menu allows you turn off wifi scanning so they make it seem but this toggle only disables wifi scanning features at user level installed apps, not wifi and GPS scanning for system based ones provided by Android/vendor/Google. Only time when wifi scanning ideally should be occuring is when you are in your list of connections making a choice to connect to. Appops is implemented into all versions of Android already at the command line level as DOS is to windows so it works as a one-time direct command adjusting permissions/settings directly and instantly, not like other apps which run receivers to trigger scripts continually draining battery/hindering function. Play Store App Ops gives you the graphical interface to utilize it easily(internally utilizing ADB at boot sequence to apply changes all at once or all can be disabled just the same if issue were to arise tweaking without research), allowing you to directly set system app and user app permissions to ignore these requests with blank data(rather than blocking and crashing app). The only select few apps I set to allow location access to is Google Maps cloned along with google play services, isolated in my cloned Island work profile for when needed , then two I set to "allow only while using the app which are both needed for IMS registration to successfully complete at boot: DiagMonAgent and IMS Service. Since IMS registration takes place only once on devices at bootup, if I have wifi left on before rebooting it may trip to Cellular Preferred only once just at this moment depending how fast wifi connects vs completion of IMS registation. So as long as I don't restart with wifi on my issue is now 100% resolved and now completely entirely non-existent, "WiFi Preferred" calling mode is now holding persistently, only now accurately displaying unavailable currently when wifi diminishes before dropping or as changing WiFi to another connection, IMS re-establishes and maintains "WiFi Preferred" option through every transition. The other guy can above can run back to Verizon if so he chooses but either way we ALL live in this Google/Microsoft driven world whom both want to know every last detail of none other than you, good luck getting them to change their ways or to get your new carrier to sell you a device that has neither but works on their network, otherwise mod your own device you personally own how you like the way, we in the free/open-source Linux community, always have. Windows 95 does still function also if you so choose to use it for something or like demonstrating how things USED to work in days of ol, but if you want to use it with today's world of software and hardware both, you won't have much luck.  If you merely buy a device from any standard Cell Phone Carrier you are in fact buying into their whole entire knowledgeably ignorant scheme to hand them hundreds of dollars only because their service is somehow unexplainably "better" than their identical competition with identical devices and consolidated shared Cell towers, sales are not developers are not technicians, continue the endless loop. Open source already fixed the problem, Google and Microsoft never will because it is 100% strictly marketing based and profiting them, if a product doesn't work well or no longer does after being updated to "latest improved software" you'll come shovel out hundreds for another new one to replace a 6 month old new one….right??? There are other forums for those carriers too once you find yourself in the exact same current situation once your new device updates itself. Also good preventative to avoid vendor forced OS updates that some have found their devices booting up to regardless of disabling automatic system updates (vendor/carriers do have the ability to and do force system updates occasionally in waves to all devices reporting not being updated after a set time duration expires pushed through SMS/GMS code in the System Update app) if using Island then freeze (disabled until YOU open it)the update app and only update once you know updates are stable, most vendors wait months after security updates are released before they push them to available for your device to see in the first place so a little extra time on your end to actually verify stability between other actual users will keep this and any other unexpected downgraded updates from disrupting life

I just got off of chat with support and have a solution that works so far. I had to have an e911 address set to keep it in WiFi preferred mode. If I had to guess, I'd say it's a safety precaution so that in the event you call an emergency number when not connected to a tower, they know where to send responders. The agent set the address for me, but I also see the option to set it yourself in the wifi calling options.

Wow, unbelievable! It's hard to believe that this is a problem with all the carriers and there isn't some kind of uprising. I am impressed that you've found a work around, but it is just too complicated for the average person (and maybe me too). Why can't the carriers come up with a solution? Of course I suppose they like for you to use cellular using chargeable data….though using wifi would reduce congestion…..I just don't get it. But, what used to be a reliable phone & service has become practically unusable! Is this progress? I would be very happy to go back to where my service was a year ago….it worked great then. Strange that they appear unmotivated to fix this. Surely they will have to come up with a fix…..and soon! …..or not!?!?

But, reading the Verizon community forum that you provided was quite interesting….what was most revealing was that apparently this isn't a problem with iPhones. I've always been an android user, but now maybe it's time to make a switch. It would be nice to see more confirmation on the iPhone not having this problem. Have you heard any more about that? I just spent $2500 on new phones (partly to correct this issue), but I need reliability! I might have to spend more (iPhones)….I just need to know my options and you seem to be the only source. Thanks for that!!!

As others have said elsewhere, this is kinda almost a global developing thing between "consolidation" of networks between massive amounts of cell service carriers further developing as they merge, anything running Android 9 or newer unless its a custom firmware/rom or maybe some early Android 9 rollouts. Been happening for years depending what you're running. Check out Verizon's status here:

https://community.verizon.com/t5/Google-Pixel/How-do-I-force-wifi-preferred-for-wifi-calling/td-p/1086338/page/5

If you have an old phone and sim thats active prior to these issues you may be in luck foe the time being but just as I find with tmo you have to start with a new sim card or when you "upgrade" with a replacement, newest are 5g compatible but features get locked out in phases in this process of which a carrier determines is no longer supported as with whats happening to 2g/3g type devices currently. People been battling it for years between em all. You can fix it yourself with the help of a pc with less a tenth of the characters in the command prompt that it took you to respond or continue to wait with the others as they have for years. Only part i get on the Verizon thing is overall coverage area, each has their dead spots so i roll with a Verizon Jetpack from work for that matter. Everything I did a factory reset clears all, my point I never reset my phone once since the day I bought it. In the long run i have a fully functioning phone with everything working, multiple work accounts syncing smoothly with all nonsense silenced, the apps I use are thouroulghly developer tested, widely used, and google play store certified. Do you really think its usefull like Microsoft and Google both branched together to do and upload every sigle device's user data to "their" cloud"? Using my phone as a PC as an IT tech pretty constantly all day, I'm satisfied with less than 25% total battery use for a usual day, probably will be a bit better than that now that I won't be redialing calls constantly and fighting between menus or missing important calls from my hospitals or schools while working at them. Yes there are bad apps out there, do your research for what you choose, Im a tech who doesn't take care in time to wait on industry and gave up on any companies status on customer support decades ago, i fix what i need to fix with proper research where needed. 

Wow! That's quite the "fix". This is far more than I'd like to take on. This problem shouldn't have to be fixed by adding some questionable app that controls all your permissions and then essentially hacking into the controls and experimenting your way to a solution….that, in the end, might just improve things (or not….or make them worse). I think it would be easier for me to just switch to Verizon! I think it's up to T-Mobile to come up with a fix….a legitimate fix….not a hack! It seems an update they did caused the problem, why not come up with a fix update? It's funny that my wife and I both had this issue starting about 5-6 months ago and now, thinking we could fix it with new phones (and sims)…...NOT….we had the exact same issue with the new phones and sims. Why OUR phones? Isn't everyone having this issue? if not, why not? Who is affected and why? This should be at the top of T-Mobile's diagnostics….and quickly! I can't wait much longer and I'm certainly not hearing anything from them. Hmmmm…..why not? I thought they had excellent service! Well, they used to anyway. I'm not happy!

EDIT: Noticed it still flipped once in the middle of a meeting. I now made one last adjustment in App Ops for Wi-Fi Calling app setting the "Change Wi-Fi state" option to ignore, and another reboot. Will see what happens but I have verified while connected to an active wifi router, I unplugged the modem, Android status bar showed internet connection not available, bounced between this and my hotspot a few times back and forth, "Wi-Fi Preferred" selection is holding through all without any other intervention or pesky notifications, also while connected to dead wi-fi calls went through no issue from cell data while my meeting disconnected looking for wifi, also stretched out my hotspot to minimal signal detecting 2Mbps wifi speed with my meeting lagging out and full cell tower bars, now this actually fits the definition of WiFi Preferred, status in call settings now only changes to "Currently unavailable" occasionally if when travelling to outskirts of actual wifi signal and re-connects persistently as Wi-Fi Preferred once in adequate wifi range, partnered with a proper mesh wifi setup seems to be working properly smoothly for once

Solved! ! ! Not certain how may people are still having this issue since Android Pie update but I think I have found my solid working fix for WiFi calling continually flipping to cellular preferred, I am on TMO Samsung S8 Active but from the sounds of things this should do the trick for many other carriers or devices if any others could please followup with further testing. After trying numerous other discussed attempts and further digging I found out all I needed was a simple tool I already had from battery saving mods, no ROOT is needed at all but can be accomplished just the same if you are. First step coming closer to making this work, I turned off WiFi scanning by searching for it in the general settings menu of android, this is to help avoid any extra unneeded wifi signal interuptions, not certain how well thia plays with any "companion device" users but may, I have no purpose for these. I use Greenify and Island to debloat/disable unneeded apps from my user interface that application manager fails in ability to do, a computer with ADB installed and options enabled for such in Developer Options, search XDA for setting these up, most of this was just for battery savings essentially and is unneeded but good help. The app I installed which I found fixes our issue is App Ops - Permission Manager from play store, using a computer loaded with ADB and dos/command prompt terminal to send commands to grant needed permisions. Once in App Ops, make sure system app options are checked and scroll down almost all the way to the bottom to find your systems WiFi calling app and set "coarse location" option to "ignore" to prevent network scans from triggering this hated event and then also set the "modify system settings" option also to ignore blocking changes from occurring. I also have coarse location on my Phone app set the same too but I don't think it matters on that app, I had set the phone app previously as such with no effect until tweaking the permissions on the WiFi Calling app itself. Using App Ops I find you must reboot also for permissions to take effect. I have multiple wifi routers setup and hotspots from work I used to try to force a change-over to happen as WIFIs change or diminish out of range(as this function is implied with its label), my WiFi Preferred calling method is now finally under control. If you choose to use App Ops to resolve this issue or expirement with the others, only use the suggested options for the WiFi Calling app, all other options I tried on it either crashed the app or breaks IMS Registration otherwise which is needed for Video/VoLTE/WIFI Calling features. Tweak/debloat any other apps you wish to save battery/data at your own risk one by one, especially any other features in App Ops, very easy to break functionality of any of these or other functions if you tweak too much all at once like I did to try to fish through what messed up something else(good thing theres a select all/restore to defaults option) tweak little by little if you do, I was one of those standing at the store and on tech support for endless hours set on it being my out dated sim card then 2 new sim cards doing the same before finding out I tweaked to many settings same day I had got my new sim card

Same issue here. The problem seemed to first appear about 6 0r 8 months ago or so after an update. I then starting missing many texts and calls both coming and going…..very frustrating! My wife was having the same problem with her Note 8. As with others here, the T-Mobile coverage here is marginal and we depend on the WiFi calling for the majority of our communication…...not anymore! We were actually due for new phones anyway so I thought, rather than try to fix the problem, well, it must be our old phones. We upgraded to an S21 Ultra and a Note20 Ultra…..$2300 worth of new phones! Things seemed good for a week or so….then we seemed to be missing texts and calls! Our phones were again swapping to "cellular preferred"! This is completely unsatisfactory!!!!  8 years ago I swapped from Verizon to T-Mobile (even though the Verizon coverage was better) because I believed in the T-Mobile customer service and extra perks. But if the phones can't perform their basic functions, and, T-Mobile refuses to resolve this issue, it may very well be time to go back to Verizon! 

Sane issue with me, having poor signal in my house, my s21 won't stay on wifi preferred.  My pixel 2xl didn't have this issue.  I'll be switching to Verizon ASAP.

The fact that T-Mobile has not resolved this issue is horrible.

But - what is WORSE - is that if any customer WHO calls about this happening on their phone, technical support CLAIMS to know nothing about it. Like the customer calling is the first one to experience this.

They sent me to Samsung, and when I told the technician about the issue at Samsung, she started laughing and said T-Mobile should be able to fix the problem...

Perhaps T-Mobile higher ups dont't know anything about it, which even reflects even more badly on T-Mobile. How could they not know with all these postings??

How can this company that spends zillions of dollars on advertising for new customers not spent some on IT to correct this problem?

Is this wi-fi issue only on the Samsung phones? I have an S9. If not corrected soon, I am moving to another carrier. T-Mobile does not deserve anyone's business with such incredibly obnoxious and stupid technical support and their being unresponsive to a legitimate issue which troubles many of us for the very same reason.  I have read all the messages back and forth -- WHY HAS THIS NOT BEEN FIXED?????