I have not experieinced that drastic of an issue. I’m sure you did the reboot thing already. When I 1st got my phone I had issues with mobile calls and data. I figured user error so I wiped my phone, not once but twice - 3rd time is a charm. Now everything works as it should with no issues. Yes, it’s a pain to reconfigure everything, but I looked at it as training.
Happened something similar to me (but only for the mobile data/calls/texts, wifi was working).. restarted the phone with sim still inside it- somehow that fixed it