MTN refusal to asssit a loyal customer

I have been with MTN for 16 years and have never had an issue with their billing or services. Last year when it came time to renew my contract i got a better deal on a phone i wanted with Telkom,so MTN gave me a 3 months free offer for being a loyal customer. I thought that was a nice gesture so i decided to remain with MTN. Since the contract started in September i have had to fight&beg everything month for them to allow me my 3 months free. I eventually received my "credit" in December only to then have my account DOUBLE debited. I have provided everything they have asked of me including bank statements for the last few months, but yet the retentions department say they can not help me any further(i have dealt with the same person every time) as "they have done their job" and customer care say i need to get retentions to assist me. I have had terrible and rude service from customer care and if i call through to retentions -my shortest waiting time so far has been 46 minutes. When i get through and use the reference call numbers provided- they say these do not exist! Furthermore the stores can not assist me and say they have no authority to log into my account-so no help there either.The gentleman in customer care says he can not provide me with a detailed bill for the last few months-showing the monies they have taken from my debit order. I really am not sure which way to go. I have emailed,called,messaged over 100 's of times but no response/feedback. I have refused to pay my account until this is sorted but of course, they have told me they will suspend my account,which i need. I am beyond frustrated!