ATT never cancelled my 3rd line

I was a client with ATT since 2007, paid my bill on time and had 3 lines. The 3rd line had to switch to Verizon over a year ago because she couldnt get signal in her house. I kept the line open since it was $10/mth to keep and I loved ATT. We recently moved from Philadelphia to Breckenridge CO. We noticed a difference in our service coverage and that we wouldnt have signal in areas that our friends with Verizon did. Unfortuntially we had to leave ATT. I called in July to cancel the unused line [edited for privacy-please do not post personal or unique information such as but not limited to full names, employee ID numbers, email addresses, phone numbers, account numbers, etc.] and tried to see what we could do to keep the remaining lines. I was told if we switch the other lines phone numbers that will turn off the service. My phone call should have cancelled the unused line 7580 and  the other lines would have cancelled when we had to switch. My ATT app stopped working with the payment alerts, options to pay ect. When I called to ask why I couldn’t pay my last bill via the app like I always do the rep said that its because my account is closed. I paid a large ~$450 bill which I was assuming and was told it was all the cancellation fees and final payment. Yesterday I received an email stating that I have a $200 bill, I may have received one prior but didn’t notice it. When I called the rep said that the 7580 line was never cancelled and that I should have noticed sooner. He said I had to pay the 2 months of unused service plus $98 to the cancellation fee and that it was my fault for not canceling the service which I was told I cancelled 2 times. He offered a $25 credit (for something that was not my error but since the “notes” on the account never talked about the cancellation it was my fault). I do not mind paying the cancellation fee as that is my fee to pay but the extra 2 months of bills is not my error. I can still be reached at the number ending in 5459. I will continue to post on message boards and blogs until this is resolved. *****