Extremely disappointed at Cell Cs legal department

I have been calling the legal department, but no one responds to calls. My contract has been settled but it is reflecting a default on my credit record. I called Nudebt and I was told that Cell C keeps on sending my details to them even though my account has been fully paid. This is creating duplicate accounts and it is affecting my credit record. I am so disappointed at Cell C especially because is no one is willing to assist. How is it possible that calls answered for hours? This is unacceptable...