Worst service and ***** in RSA MTN

Good day

This is completely unacceptable. I cancelled my contract with MTN on the 9th of March and still, they took a debit order. I am even unable to reverse the debit order. Their service has been and always will be the worst of any company in RSA. I went to them to even ask about my contract I signed with them for R316 because they took for two months more than R500. Their reply was I am lucky that they only started now to take more per month.