Xfinity customer service says it's a device issue and Apple care says it's a carrier issue. iPhone 6 that was working fine until it just didn't. Considering switching carriers to solve the issue.
Hello tm772, I am sorry to hear you are having issues making and receiving calls.
A good troubleshooting is to reset network settings on your phone by:
Tapping Settings > General > Reset >Reset Network Settings
If the problem persist, I would like to take a closer look at your account. Please send me a private message with you account info and the phone number you are having issues with. To send a private message, first click on my name "ComcastTito" and then click on "send message".