Dissatisfaction about account settlement

I had a loan with capfin which was in arrears and was handed over to their legal department for collection. In 2015 September I settled this account with the legal department who then sent me a letter confirming that the account was paid up. I forwarded this letter to capfin as they kept calling me demand that I pay. To this day this matter has not been resolved. I have spent a lot of money on airtime trying to sort this out without any success. I have been transfered from department to department and no one seems to have any knowledge as how to help me. This is such an inconvenience in my life. It's a stress that I don't need. Now they say I must wait another 7 days. For an account that was settled 2 years ago. How is this my fault? M really frustrated with this company right now.