Sadly same issue form me (Poland, Orange). Using iPhone 15pro, setting to just LTE doesn‘t solve the issues, cannot install 18 beta 5 because installed 18.1 which also doesn’t fix the problem - which I hoped it would.
It seems that the issue is outside the US?
The stacks files in analytics states a baseband crash detected at random. the stacks files shows up when this error occurs.
I sent feedback but investigation was completed with the status that they are unable to diagnose this issue with current information. I attached 2 new stacks files with this error. Dunno if they will be checked.