Can Someone tell me if there is an email address for billing support?

My elderly mother tried to cancel service and was not able to get any help at the T-mobile store because she was not in possession of a PIN number. If she ever created one she no longer remembers it. She switched to Xfinity and now she can not access the T-mobile website to use it to cancel because it asks to verify phone number as part of login. I don't see a way to get in contact with billing support at this time because when I call they will not take a call only refer me to automatic pay over the phone. I would like to send an email canceling service. My mother switch carriers July 10 2023 but is still being billed since then.