No Service after they did not close account

Went to apply for a phone contract and they inform me that there is a Standard Bank credit card on itc. I paid up the account over 12 year back and asked them to close it. They never did. Never phoned me to inform me on the outstanding on the account and hand me over to DMC and list me on itc. Went to the bank and they told me to get in contact with DMC. DMC said they will investigate and infor me on the outcome. Now they informed me that the it is been writed off . They send me a letter with a reffrence number on. Now I need a paid up letter with the account number on. Standard bank said I need to get it from DMC. The lot at DMC dont give you a service and keep on dropping the phone. Why do I need to do everything? Standard Bank did not close the account and handed me over. Why can't the bank and DMC sort it out. I need my name cleared from itc and nor the bank or DMC want to assist me. I really think it is very poor service.