I recently brought my pixel 3a to Xfintiy Mobile. One feature I loved from my previous carrier, verizon, was the carrier video calling option, built right into the phone's dialer. The option to turn it on has not appeared on Xfinity Mobile though. On their info page, it says that they support carrier video calling on Android, and when I chatted with thier support staff, they also said that my phone was compatible, but could not figure out how to turn on this feature. They sent me to google support, who sent me back. This problem is true for all the andorid phones on our plan.
I am interested in this too. I also have the same problem with the two Pixel 2 XL's on our Xfinity Mobile plan. This feature was working fine while we were on a direct Verizon plan, but now the option is grayed out in the phone/dialing app and the video call button doesn't appear during a phone call either.