Telkom account Error is now MY problem

My land line account was closed in July 2018, there was a credit due to me. JANUARY 2019 - The error was with Telkom, they incorrectly processed an amount as a debit NOT a credit, listed me as a bad payer (I NEVER received the information) this was corrected in APRIL 2019. JUNE 2019 I have been listed with the Credit Bureau. -Now I must request a clearance letter for their error. First request was 24/4/19 then 13/5 then 30/5 then 04/6 I was told 48 hours I'd have the letter. Phoned again on 07/6. The call center are disempowered! They can NOT assist.