The Android 11 update came out on May 10th.
This seems a strange problem. After updating to Android 11 there have been various problems relating to calls (low volume on Bluetooth, audio going to the loudspeaker instead of the earpiece, …) but I don’t recall having seen this one before. Also it’s not systematic. Just a few ideas:
- Is 4G Calling enabled? If so, maybe enable / disable this (might be helpful in some areas and not in others).
Go to Settings > Network and Internet > Mobile network > 4G Calling - Is there a SD memory card installed? If so, you might try removing it for a while.
Make sure it’s formatted as “Portable” / external. - Hardware / poor antenna connection. Has the phone been dropped or encountered some other physical shock?
- Changes to or problems with your carrier’s infrastructure. You could ask around if other subscribers have noted similar problems.
To go any further we’ll probably need more details. Does this always happen in the same places, at specific times, calling or being called by certain numbers, etc.
It might be useful to know exactly which software version you received: 8901-4.A.0010 or 8901-4.A.0011. To find out, go to Settings > About phone > Build number.