Weak Service, No Help

I left Verizon a month ago for Xfinity. I'm in a 5g zone for Verizon. I bought a new Samsung 24 FE. The signal strength the phone receives is so weak it drops calls, including from my doctor. I am a cancer patient.  I need a phone that works.
I have wasted twelve hours in chat with customer service people. They have put me through all of the steps of troubleshooting multiple times, including twice giving me a new e sim. Nothing works. BUT every time at the end of the contact, I am assured that the advanced team will solve the problem REST ASSURED within an hour.  If they need me to do anything they will email me. Obviously that was untrue. All week no one has contacted me, nor fixed the service issue.  There is no point in contacting them anymore. 
I have been given MULTIPLE CR numbers assuring me of a fix within an hour. It has been a week. Nothing.

How can a customer  (38 years of cable, decades of internet, and a new phone of yours)  get someone to take this issue and get it fixed?  Is there no hierarchy when service fails?