BAN invoice account

I have a toll free number with an Invoice BAN number and 1 phone number on the account. This only bills long distance. Originally, there were about 3 numbers on this account that were ported over to other plan with ATT. For some reason, this number was left behind and kept accruing costs. I've been on the phone several times resolve this. No one I've spoken to is able to find this account using the BAN or the phone number and I've been transferred to other ATT reps who also have no idea what to do with the BAN number. I visited the store also for the help but all they can do is take payment and are not authorized to see full details of my plan.

I want to see why I am being charge so much for the Toll free num while it is being used for few call only.

Can someone help me from your department?