WiFi Calling Not Working

I brought my iPhone Xs Max from AT&T to Xfinity yesterday. New sim installed, Shows LTE, everything else appears to be working, but the WiFi Calling.

It’s a loop... I toggle the WiFi calling; enter emergency address, once finished, I go back to check on it and the WiFi calling has been turned/toggled off.

I have tried Reset All Settings, Reset Network Setting and Erased All Content and Settings.

None have helped.

I have called Xfinity Mobile several times, just so they can tell me "Wi-Fi Calling is on by default on your account." I am not getting anywhere with them, and the store does not have the Mobile staff on hand right now.

I really need this WiFi calling to work. Please help.