Contract Cancellation not completed in time and no refund has been received

Have been trying to cancel a contract since March 3rd I have called 6 to 8 times (once a month) and spoked to 6 different people to get assistance. The contract was not cancelled on time and I am still being billed. I was told that I would get a refund, this has not happened Today I have called again to ask what the situation is and how can it be that this has not been resolved for 6 months. Pathetic service, does MTN stand for Most Terrible Network?