Clear name on ITC

Cell c has the most poor customer service ever I recently found out that I had a debt with cell c and it has been carried over. I then called the company that purchased the debt and settled the account. I was informed it will take 21 workings I been calling them almost everyday they from on getting back to me didn't even get a paid up letter. I can't even buy a car or get my child to a good school because of that. .