Charter Communications are trying to steal money from me.

I have had a Charter account at 3 different addresses. I am currently up to date on my payments, yet, today, I received a letter from a collection agency stating that Charter has sold my account to them and that I owe $57.42. Upon calling customer service, I was told that this is an outstanding debt from over TWO YEARS ago! Each time I have moved and transferred my services, I have told the teller at the local branch that I wanted to go ahead and pay whatever I owe before closing out that account. I have been late on payments here and there, but always pay what I owe, and am current with them right now. Customer service says that the account has been sold to the collection agency and that they cannot help me with it. I am left with no choice but to contact the collection agency to dispute this debt. I can not believe that Charter would risk losing a customer who pays them over $140 a month for services over an obviously bunk $57.42 "debt". If I cannot get satisfaction soon, I will be canceling all of my Charter accounts, and reporting this to every consumer activism Website I can, as well as the Better Business Bureau.