Will my Sonim XP3 work after July 1, 2022?

I also have a Sonim XP3 that I upgraded to from my beloved old Kyocera DuraXT around the time of the Sprint merger because they told me the DuraXT was incompatible with the soon-to-be-upgraded network.  I explicitly chose the XP3 because it WAS supposed to work on the upgraded network.  A couple months later they sent me a letter in the mail telling me I had to "upgrade" again.  After sifting through multiple mixed contradictory messages, I figured out that the XP3 would work IF the VoLTE option was enabled.  The reason why 3G phones had continued to work is because of delays pulling the plug on the 3G network, which now is scheduled for July 2022.  The XP3 definitely IS capable of doing Voice over LTE on the new network, but you have to enable VoLTE to get it going over 4G on the new network.  Settings / Network & Internet / Mobile Network / Voice Networks / VoLTE calls - it'a a toggle switch, and it's greyed out if you're on a call.  You have to be disconnected from all calls before you can turn it on.  After you turn it on the indicator on the top of the screen immediately to the left of the signal bars should say "VoLTE" with "LTE" also above the signal bars.  If it says "3G" you need to turn it on or the phone will no longer be able to make and receive calls whenever they finally deep-six the 3G network.

That said, I am still having problems sending and receiving MMS (picture) messages on the XP3 over T-Mobile.  SMS (text only) works fine.  MMS used to work with this phone.  Last MMS I successfully received on it was on 05/05/2021.  I currently have support tickets open with both T-Mobile and Sonim on this issue.  In the meantime I just tell my contacts if they want to send me pictures, send them over Telegram or other instant messaging apps that I can access from my computer or tablet.  Most of the MMS I get these days seems to be from political fundraisers who just want money, and they can go to /dev/null anyway AFAIC.