Post IOS 15 update - No Sim Card Installed

Ever since updating from 14 to 15, I believe I went directly to 15.1, I have been sporadically receiving error message "No SIM card installed", after which the service on the phone will promptly disconnect me from wireless service. As you can imagine, these is incredibly frustrating, considering I pay over $100 a month for this iPhone 12 pro and all of its high-speed service.

So much for waiting until the version had some legs under it... Thanks Apple. I hate updating my phone, as something Always gets worse or breaks...

I had hoped that updating to 15.2 would fix this problem, and yet it seems to have only altered it. Instead of having to reset the entire phone (as I had to do initially), since x.2, no it will reset itself within a few moments.

Still, it breaks any phone call and all service to the phone while this is happening.

I have reset network connections, and surely have restarted the phone a half dozen times.

Anyone have any experience, advice and hopefully, have found a solution?

Thanks so much for your help!

ps. I changed absolutely nothing. Not a thing, but simply updated the phone. Therefore, it should have absolutely zero probability of it being a hardware problem. The Sim worked fine for the prior 14 months...