Won't clear my name/account

I paid off my account in January 2017, together with the jewelry insurance. I still get a statement every month stating i owe about R20.00 which has been escalating every month. When i call to resolve the mess, I am either told that they have "properly closed my account" and that i should not worry. They still fail to provide me with proof of payment. My credit score has been negatively affected. I hate TFG! I get told to call after the 13th, when I do i get the same old stories