Wrong information on the credit burea

I am applying for a homeloan. And according to the bank I have a dispute against my name from cell c. I am R2153 in arrears for a contract closed in end 2017. I have been trying to phone Cell C legal department for the past 3 working days just to have a voice message saying that they have a technical issue. According to the call centre I dont owe Cell C anything. Now I need to wait for a paid up letter which can take anything from 7 to 21 working days. That is just unacceptable. I need a paid up letter ASAP for a mistake Cell C made. I dont have 7 working days to wait for a paid up letter.