Cell C bad customer service

I had 3 Cell C contracts and have settle all of them. I did receive all my paid up letters from Cell C.

I keep on phoning them and keep on getting different answers. The first one " I can help you because you failed your credit check with the questions ask" 2nd one "You need to email your paid up letters to the credit bureau yourself because there is nothing we can do".

I'm trying to buy a car and find this very difficult because it shows I have missed payments and this is a bad reflect on my credit record.

I really don't know what to do anymore, it's so frustrating:(