Paid up letters please.

I had an account with Cell C which was handed over as i stopped paying it due to unhappiness of the contract. Therefore I was harassed to pay for it by their collection agency(Blake), which i eventually did. Its been almost 30 days after i have settled the account, i called the agency to confirm if my payment was received and they confirmed, and i requested for a settlement letter immediately and they promised to email it to me. I have not received letter so far. I sent email but no response. I called Cell C legal department but no help except promise. Even now no settlement letter and balance still remains at Credit Bureau.