Worst service provider MTN

Ive had my contract with MTN for the past 5 to years and only last year I started experiencing debit orders that I didn't authorize in my account from them..I had to dispute this every time it occurs. Worst part is that they initiate on dates which I don't get paid on or have money..this has affected my credit record badly and even now am experiencing the same nonsense..ive going back and forth with their consultants and the only thing they can say is " the system can't change it"..debiting as a 3rd party without clients authorization is *****.