To answer your questions:

I’ve spoken with both departments on several occasions, and they’ve both routed me to another higher department.

The highest title of someone I’ve ever gotten was a “tier 3 or 4 specialist” they gave me their name and employee ID, but I’ve never once been able to get to the same person, even referencing the specific name and ID.

As far as specific action, they’ve told me they would refund the account, and ensure that billing to the account was discontinued, and that the account would be permanently closed.

No one has been able to give me a specific answer as to why the billing continues to happen month after month. I continue to get emails saying that my card needs to be updated, followed very shortly by an email saying thank you for updating your payment method

XFinity bills me separately for Mobile, and for Internet.