What do I do about my iPhone giving "Unable to Activate" message, and asks for "an update is required to activate your iPhone." It is basically a brick now, and I cannot make my phone work now at all.

I began to experience cell service and cellular data issues a couple of weeks ago. My 12 Pro phone is approximately 9 months old. My wife's phone is not having issues, so we know it isn't a service provider topic. I got a text message from Apple saying to try to update my software again (which I did in the last couple of weeks). The only way I could do this was to do a system restore, since I could not make my phone update. When I did this, it made my iPhone useless. I had backed up my phone to both the cloud and MacBook prior to attempting this. Now I have tried to use both my Mac and WiFi to make my phone update through iTunes, and I get an error message on the Mac saying my phone activation could not be done. What do I do? I cannot get any further than what I'm doing.