Charged Off Loan

My car was repo'd by Bank Atlantic and charged off in 1993. According to my credit reports, it was stated that it would remain on my report till Nov. 2000. The bank sold the car at auction and although I have never received any credit for the amount they sold it for, they added lots of extra charges to the bill. I have never paid it because I had lots of unsettled issues with the fake warranty from the dealer who sold me the car.

I have since straightened out my credit which is current and paid on time. Recently I applied for a mortgage and was told that one of the 3 bureaus, Trans Union, is still reporting it as an outstanding balance of $3600 (but it's not shown as a repo). The mortgage company now wants me to pay off the debt in order to approve my loan. I believe the debt was probably sold to a collection agency although I've never received any demanding letters. Is this problem fixable and who do I contact?