Experienced something similar on Pixel 9a. Temporary fixed it by disabling 4G calling in:
Settings-->Search for Calling
My settings are now:
- 4G calling disabled
- Preferred network type 5G recommended
- Wifi calling enabled (call over mobile)
This works for calls, but I think I am not using VoLTE now?
I assume so, because when I switch Wifi calling enabled to be over Wifi, I can not see any requests in my opnsense firewall.
However, I also tried with Preferred network type 4G and 4G calls enabled but this didn't worked - it seems whatever settings I use with 4G calling enabled calls do not work.
Would like to know which of the mentioned settings are the VoLTE settings and maybe the settings above help others to temporary fix it. However, I assume this won't work forever, since non-VoLTE calls are going to be disabled in my location.
Temporary the settings are ok for my threat model, since I usually even do not use phone calls anyway, but be aware that I guess VoLTE ist this way disabled and adapt this to your threat model please.
Any permission settings did not helped in my case.