MTN not refunding my money.

MTN made an extra debit order from my account after I already paid my final contract amount. This occurred at the start of June already. I asked them to refund the amount to me. I have been in communication with them via email and on social media for over 5 months now. I have had to provide the same information to them multiple times. Every time I ask them to sort out the issue and refund my money, they always just say they apologize for the delay and they are still attending to my problem. How is it acceptable that that has been the excuse for months now??