MTN frausters, Bad Customer Service. Don't know how to treat their customers

MTN is *********, I had a contract with them and it ended on the 15/5/2020. but they still deduction money from my account without my consent. I went last month I went to South Gate Mall MTN to ask about the matter, the consultant told me that he cannot check for me on their systems since they are not allowed to check for the customer, but I must know that MTN will keep on deduction from my account if I don't cancel the contract with them I was shocked to here that because They must stop the contract immediately after it finishes. The consultant didn't help me at all, he said I must do that myself by dialing 135 number of which no one answers that number their prompt doesn't give you the option to choose to speak to the consultant from MTN. Bad customer service at MTN. I want my money back that was deducted in June and today (July) despite sending them an email to cancel the contract they deducted again. Bad service indeed.