Deactivated/Non-Existent Bank Account Still Being Charged Somehow

So I recently switched banks and deactivated my old bank account. I paid my AT&T internet bill a few days late (no late fee was issued to me on my end) using my old account by accident without even thinking, definitely my mistake.  It got denied, obviously, and I was charged with a returned check fee and a late fee (I would like to point out that I did not receive/have a late payment fee at the time of making the late payment, although it says the date of the late fee was a day before I initially paid...very strange).  When they finally emailed me and notified me of what had happened I immediately went into my AT&T account to find that the old bank information wasn’t even saved in the payments options anymore, which was fine with me. I proceeded to enter my new and correct bank information and saved it, also got a confirmation email that this was done. I then continued to pay the late/declined/returned fees and the entire bill itself with the new and correctly entered bank account information. I checked my emails, and my bill receipt online, and they both say that I tried to pay with my old bank account again!! The information for the older account isn’t and wasn’t on the website at the time of the second payment. I would like to point out that I am NOT on autopay either, I pay manually each and every time. What is going on here and what do I about this?? Now I assume that I’m going to have another declined/returned payment fee and an even bigger late fee! Something is seriously wrong here. I would go into the AT&T store now and see what’s up but they are currently closed where I live and I will have to wait until tomorrow to try and fix this issue.