Infuriating Situation

An account for a property my company manages was cancelled in April and a confirmation number was provided. Except that apparently it wasn't cancelled on AT&T's end. Months later when this was discovered and after invoices had still been paid, we called back and were told they have no record of the cancellation. This in itself was unacceptable but we were told, again, the account would be cancelled and were given another confirmation number. At that point AT&T owed us a few hundred dollars at least, but no one would agree to that because they had no record of the previous cancellation. After hours of being on the phone trying to resolve this, it wasn't worth a further fight trying to collect that money. However, after all this started in April 2022, we STILL received a bill in September that has now been sent to collections! I don't even know what to say at this point and your employees that were once responsive have said they can't help us. I emailed them back and asked for contact info for someone that could. Naturally, no one has responded. I'm pretty sure I don't need to point out that this is beyond unacceptable and AT&T needs to do the right thing and refund the money paid after the account was closed the first time.