Phone call sounds garbled and robotic

I know this thread is old, but I have this issue all the time and I'm on the verge of needed to move away from T Mobile.  I'm actually on a conference call right now (for the last 30 minutes) and it's happened 4x.  Audio pauses, then goes very deep and slow until it "catches up".  Is there a known issue and fix?

I have been having this exact issue and it has been driving me insane!

It began approximately 10/11/2021. Has continued through 10/30/2021.

 Locations include but not limited to,

Warrenton, Clatsop County, Oregon

Portland, Oregon

Astoria, Oregon

 Beaverton, Oregon

 Tigard, Oregon

 Hillsboro, Oregon

Timeline of events:

 Received phone back from Apple after repair of camera 10/11/2021.

Symptoms began around this date after making and receiving some phone calls after receiving the phone back from the Apple repair center.

 Apple Store Washington Square Genius #1 (Bianca) unable to determine what hardware or software issue might be involved on 10/25/2021. Internal diagnostics found no hardware or software issues with the device. Apple Genius requested I perform a Network Reset. Unable to open an AppleCare claim because no device issues were discoverable to send the device in to the repair center in Elk Grove, California.

Contacted AppleCare by chat with support 10/29/2021. Apple offered Express Replacement Service with a device value of $1,149.00 and a hold placed on my account until device received and inspected by repair center. I decided to decline the Express Replacement Service and commuting to go through the Apple Store and attempt to involve T-Mobile Customer Care.

 Contacted Apple Support by phone 10/29/2021. Apple representative was able to hear the distortion on the line. Directed me to schedule an appointment with the Apple Store. Appointment available soonest at 5:50 p.m. 
Told by Apple Store Washington Square Genius #2 on 10/29/2021 that I need to talk to my carrier. Carrier (T-Mobile) so far unable to offer any assistance.

 T-Mobile retail store operated by Exclusive Wireless 10/30/2021 manager Brandon able to reproduce symptoms, replaced SIM Card. Was unable to get carrier services to authenticate and/or connect with the device with a replacement SIM.
He updated the device to the latest software (from iOS 15.0 to iOS 15.2). No improvement to call quality.

Opened a third case by phone with Apple at direction and supervision of the T-Mobile retail branch 10/29/2021 under the device's Limited Warranty. Directed to schedule an appointment and bring in under the failure of the device under the warranty.

Apple believes that this is a network related issue through and through.

 Symptoms:

 1) Making and receiving calls

 a) Distorted audio (when both sending and receiving audio on calls)

b) Robot voice receiving audio

c) Voice Changer sound receiving audio

d) clicking/tapping sounds receiving (other end also heard the tapping and connection quality issues

e) repeating syllables receiving audio, whether live or automated 

 Frequency of Symptoms:

Daily, almost every incoming call or call outgoing

Occasionally this does not occur, and there are no symptoms and no sign of any issues whatsoever. Usually this is when demonstrating the issue at the Apple Store. Occasionally call audio quality is fine and eventually turns to shit after a few minutes of being connected.

Audio from other sources (Spotify, etcetera) unaffected.

Facetime working without issues (FaceTime audio and video): Yes

T-Mo!

Please resolve. I have two devices on contract purchased new from T-Mobile this year. Credit Class B.
Would appreciate a full resolution.

I have documented this with recordings available of my calls.

Gracias

Well that is no good at all! Is this a common occurrence or is this the first time? How many bars of signal does your phone show that you have when this happened? 

I have been having this issue as well. The phone will be stationed in one place and I will experience this.  I also could be holding the phone standing still and if I move my hand the call becomes distorted. I have a Note 9. It's extremely frustrating because I miss parts of a conversation 

Hi - I had something very similar happen today and got it resolved, so I found this thread and thought I'd add my experience to it. 

I have a OnePlus 6T McLaren Edition which has always worked perfectly on TMobile since I got it in January.  This evening, I was trying to call a local business, and he kept saying "I'm sorry, but I can't understand you. You'll have to call us back."  And then he'd hang up.  It was odd, because I could understand him perfectly, and I had full signal strength and had turned off wi-fi so that I didn't have any potential issues with that as I sometimes do.

After calling him the 2nd time and him hanging up again, I tried calling my own work cell phone, which is on AT&T.  It rang and I answered it, and as I spoke, I understood what he was talking about. I sounded like a robot spitting out random crackling sounds. There was no way to understand a word I said.  I immediately restarted my phone, and that had NO EFFECT on the issue.

I wondered if something had happened to my microphone. I tested with my voice recorder app, and that was crystal clear. No crackling or distortion at all.

I live right down the street from the T-Mobile shop, so I popped in a few minutes later and asked one of the guys if he could help.  He tested with me and verified the issue, and then he did something to "reset" the actual phone application on the device. After he did this, it started working again.

Chris, I don't know if you still monitor this thread, but this happened to me again today.  I chatted with OnePlus support (I bought my device directly from them since it's a McLaren 6T) and they had no clue.  They had me wipe the phone's cache by rebooting into a special mode.  That didn't work.  The only thing that works is clearing the STORAGE of the actual phone application. Not sure what could be causing this.

All these posts are great and might help if you have a new phone, but for old android phone, it doesn't sound promising. After the last update to Andriod 10, our work phones start performing weirdly, like garbled, choppy, or robotic. This issue happened on Nokia 6, 7, Samsung, and  MI A. the only common is software and carrier, which is (T-mobile) - Trying to knock things down and see what caused this. We have replaced three phones and so far working well for the new phones. not sure if the data signal doesn't support the old phone after updating the software, or the software not fully compatible with the old phone 

I discovered this thread thru Google search and experiencing the same problem.  Any solutions from T-Mobile?

I've been having this issue for a month now and it happened again today when my wife called me at 6:10PM CST. Hanged up and called her back at 6:15 PM CST and she still couldn't hear me but hear a robotic voice. Have to reboot my iPhone XR to make it work fine again, my wife has the same phone and on the same T-Mobile plan as me but no issues for her but my phone is having the problem. 

Any resolution or suggestions from T-Mobile support? 

I've experienced these same issues. It's going on nearly three years for me. It's very sporadic. I've been in the store and asked for help, but their advice didn't resolve the problem. I then bought a new phone and am now experiencing the same issue with the new phone. Strangely, my partner who's on the account hasn't experienced any of these issues. I also don't have issue when I call her. I only have issues when calling or receiving calls from everyone else, but infrequently. Maybe 1 out of 10 times...