Incorrect charges after seasonal hold and cancellation

I'm hoping someone from Xfinity can review the final bill on my elderly mother's account.  I am an authorized representative for her.  

On August 6, I called Xfinity intending to cancel her service because she had moved out of her apartment.  The representative suggested placing the account on a seasonal hold instead, in case she was able to return to her apartment.  I agreed based on the representative's explanation that doing so would not result in additional service charges while the account was on hold.

On September 11th, it became clear that my mother would not be returning to the apartment, so I called Xfinity and specifically requested that the service be permanently cancelled.  I was instructed to return the equipment to a local Xfinity store, which I did.

Her final bill now includes $55.71 in "Services Added" for September 11-September 24 for Internet Plus Basic and TV Box + Remote.  My mother was no longer living at the apartment, the equipment was returned, and I never requested that her regular service be reactivated.

I called customer service about the charge and was told it occurred because the account had been on a seasonal hold rather than simply cancelled.  This is particularly frustrating because I originally called on August 6 to cancel the account and accepted the seasonal hold only because it was offered to me by the Xfinity representative as an alternative.

I would appreciate if someone could review the account notes and, if available, the records from my August 6 and September 11 calls.  I am requesting that the $55.71 charge for services that I did not request or intend to reactivate be credited.

Thank you for your help.