iphone 12 Pro poor signal no service dropped calls

[BocaLola]

I'm at my wits end....I've tried everything, called Verizon who claimed they had someone come to my area and check tower coverage apparently it is fine. My iPhone 12 Pro drops calls, has failed calls, signal drops to 1 bar and people can't hear me and lastly my favorite....you are not connected to service. We have 6 of these phones in my house and only 3 have these issues so it can't be the signal. I work from home and making a phone call for work is almost impossible, I can't even call Verizon support because it breaks up too much! Is anyone else experiencing these problems? If so, please let me know what you did to fix it. Thanks in advance for any help you can provide.