Unable to produce a paid up letter

I had a contract with Telkom which I paid up however its still reflecting on my credit score that I owe them, I have requested a paid up letter so that I can resolve the matter as its messing up my credit record, However each time I call in I am being told that its being escalated and its 3 years now and still no assistance. Last Time in June I called spoke to the Team leader by the name of PaulMaphoto and manager Lorren Van Wyhe still no assistance