Telkom Billing Department

I have had mobile contract with Telkom from August 2017 and since then they have given me nothing but headaches. They refuse to debit my account or send me statements. They have now sent my account to Nudebt twice even though I don't owe them anything. I paid Telkom directly via EFT and paid Nudebt just to clear my name but they still sent my name to Nudebt again, if I check the statement, I don't owe them a single cent. I have tried to resolve the matter with no success. I am getting fed up now because they are tarnishing my name.