MTN BlackFriday deal gone BAD

I took a BlackFriday deal at a store 2 years ago. The contract term came to an end. I had been trying to contact MTN retentions for weeks throughout January only to be put on hold for hours and not get through. It has been an unpleasant experience and to make matters worse, whilst I have been trying to contact MTN, I see a debit order go off my account for R1600. This made me furious because now MTN was taking unauthorised money from me. I go to the Tygervalley store here by me and they tell me it is my new month to month amount which is outrageous. NOBODY from MTN called to inform me about this change in premium. The lack of communication has resulted in this overlay of time trying to upgrade my line vs month to month enrolment. I need to get that money back as I cannot afford paying 1600 for a contract which expired. I have been a happy client for years. Please assist me with getting help from someone at MTN as I am fed-up of trying to speak to someone at the call centre. I do not want to have the Month to Month option on my line.