ABSA BANK won't acknowledge loan settlement

Took a loan with ABSA many years ago. Paid it off in full about 5 year ago. Realised to my shock that they are still sitting on my credit record as an unpaid loan. This is adversely affecting my credit score as I am on record as a bad payer. This is so unfair seeing that they received proof of the settlement at the time that I made the payment. I no longer bank with them because of other instances of poor service.