iPhone 14 Pro Max Activation

I am not being able to activate my 14 Pro Max. My carrier is Xfinity Mobile. I went to their store to activate and they could not do it. They tried to convince me that it was an Apple bug and that Apple will soon fix the problem. I did not believe them and left the store pretty upset. How can I do it from my computer? I do not want to change my number.

Thank you.

Lucio Oliveira.