Final detailed mobile bill

I recently moved to another state that does not have Xfinity so I had to cancel my account including my mobile lines. I am trying to get a final detailed bill from Xfinity that shows a breakdown of the number of payments made (e.g., 12 of 36 payments) for each mobile device in addition to the final balance owed. I have called customer service multiple times and either they don’t understand the request or they promise to send me a final bill which never arrives. I also had a friend go to an Xfinity store in the state I formerly resided in only for them to be connected with an agent online who opened a ticket and immediately closed it without resolving the issue. I have no idea what to do at this point as customer service has been been absolutely useless.