Overcharged

My monthly payment for my services is $78. I made a payment on October 1 of $102. It wasn’t until a full week later that Xfinity said my payment was returned but my bank said that the transaction was never attempted. This is not the first time they have done this. The current amount my account shows that I owe is $269 after they corrected the $30 return payment credit. Again my monthly charge even for 2 months still would not add up to $269 if each month is supposed to be $78. For 2 months it would only be $156 in total. That is $113 in extra charges that are unaccounted for. But this amount owed is only for October as my app says November payment is due on the 28th. So I am being over charged $191 for one month. That is ludicrous! I was told by a supervisor that they were going to correct what is owed on my account to my monthly rate and I was going to get an email outlining everything. I have the transcript for this conversation. Nothing was corrected, and I never got an email. Now they are demanding that I pay at least $115 out of the $269 to even speak to customer service.