Bad service from MTN South Africa

Bad experience from MTN. at this stage i wouldn't advise anyone to subscribe to their services. I had a contract with MTN and i closed it and in the process, i overpaid them. they are able to see on their system that i overpaid on my contract and i submitted the documents they requested but they are not paying back what is owed to me. it's been over 40 days waiting to get my money back and when i call i am being taken from pillar to post. Bad Service