Stop debit order

Completely dissatisfied and appalled with the service rendered by MTN. My contract ended in March this year, but ran on a month to month basis. I tried to contact MTN via their customer care line on numerous occasions but would hang up after spending hours holding on for someone to answer. Eventually I went into their Branch at The Glen Mall, where I was assisted and assured that my contact was cancelled and that I would be switched over to prepaid, I even paid for a sim swap. To my surprise MTN conveniently continued to debit my account, I tried to contact them again via customer care but still no answer. I then went into my branch to reverse their debit order, and finally some sort of communication from them, a friendly sms reminding me to pay at the end of July. Please MTN contact me and cancel my contract or I will contact the National Consumer Commission