Billed for Xfinity Mobile when never ordered

I have been incorrectly charged for a mobile account I did not sign up for, nor use. The line has been successfully canceled, but I am being penalized with an overdue balance for a period when the line was never used or activated. I need an agent with Tier 2 authority to backdate the cancellation date to the day it was ordered and perform a ledger correction to wipe out the invalid past-due balance and any associated late fees. I have already spoken with customer service and chat on multiple occasions since April with no resolution. I have also contacted my bank and filed a charge dispute for incorrect charges on my card on two different occasions for these services I did not request or use.