Cell C Contract Phone

I had a contract phone with cell c till last year November 2018 when I paid the settlement amount. After 2 months they started to debit the money for phone and decided to reverse it, so now they listed me as a bad payer on some of the credit check companies. I am asking for a paid up letter they telling me i will get the letter after 3 days while other companies can give out a letter same day! I am so ****ed off right now!