No refund forthcoming after many many calls

I keep being referred to a third party for a refund even though MTN debits my account monthly. Please contact me urgently to arrange refund, as the third party (Summer mobile) is beyond useless, don't answer their phones and don't even try to help when they do. This company caused me to leave MTN after many years they are that bad. As I will not get my money back from them, and my account was debited monthly by MTN, I expect MTN to sort out this mess with the duly authorised representative.