Contract not cancelled after sending cancellation documents

Im so disappointed with Telkom, I took out a contract with Telkom when the contract ended I cancelled it as advised by call centre and went on a prepaid option. Two years later I pins out I was black listed for R500 that Iowed on a contract I had cancel I decided to make a payment in order that my name may be cleared. I was told I would get my paid up later and two years later I still have not received my paid up letter for a contract that was cancelled, how twisted is that. This is now affecting my credit scoring as I've been sent from pillar to post everyone I call.I will never work with Telkom ever again they are such ****** I hate this company....DO NOT EVER TAKE OUT ANY CONTRACT WITH TELKOM ITS A TRAP