Account was cancelled and phone ported to another carrier, yet phone still shows Xfinity Mobile as Network & Carrier

Even though I have cancelled my account and been picked up by T-Mobile, by phone is still showing "Xfinity Mobile 54.0.1" as the Carrier.

I have a balance of $4.66 from the current (cancelled) month and I want to pay that off in hopes that it will fix the problem.

Thank you,