GrapheneOS Hello. I am one of those who have been affected by the latest GOS update on Pixel 5a.
I am unable to make calls and all incoming calls go directly to voice mail. Making any call results on an abrupt Call Ended. No tone, no ring. Just shown the active call blue screen. Call Ended and hangup sound.
Carrier does support VoLTE and never had issues till making calls with LTE Only.
First time that the whole calling system stops working in such a way that rebooting, pulling/reinserting the SIM card had not fixed.
EDIT: I did called carrier thinking it was their problem. They could not help me. After a while what I was told was to contact the phone's manufacturer and have the phone unlocked. This makes no sense to me Pixel 5a is a carrier unlocked phone and this phone since day one has was activated and has always been used with the same carrier. SM.
I guess the "locked" they see has to do with whatever GOS change is affecting the Pixel 5a.