GrapheneOS
Okay, after reading your status info I have made test calls and texting with my Pixel 9 Pro XL with newest release:
I am ever using 5G and if not available then LTE. I never use 2G, this switch is permanently off.
So my calls are ever VoLTE (Pixel phones in Europe cannot use 5G SA for calling because of Google :-( ).
(SIM cards from German providers – no 3G available – I only mention it as a precaution)
- Flight mode switched on
- WLAN switched on, using my Pixel 7 Pro as WLAN Hotspot as usual
- made a call (Time announcement service, because at this time early in the morning I don't wanna wakeup anyone)
- sent a few texts as SMS to my other smartphones (via WiFi connection)
- answered the successful sent and received text messages (SMS) via mobile radio to my Pixel 9 Pro XL
- switched off the flight mode to make a regular VoLTE call via mobile radio (Time announcement service again)
Conclusion: everything worked as it should.