Unauthorized debit orders. Unable to reach billing department during office hours

What is it going to take for Telkom to leave my bank account alone really. I now understand why it is impossible to get through to their customer care line. They simply don't want to deal with so many irate customers because they know their service sucks. I cancelled my contract months ago . What do you mean I am still being debited by Telkom what for. Wait they will claim that I had unpaid debit order . Which again doesn't make sense because my account is up to date and the debit was ran in the month of May and was settled. I now need to be inconvenienced to change my bank because Telkom won't let me have peace. My service number was ***. I this company goes down and loose all current and potential subscribers. Because It has to be the worse of them all