Unauthorised Debit Orders

I have never experienced such defiance in all my years of dealing with service providers. I cancelled my contract with Cell C on 18 February, paying the required settlement amount directly into their bank account. <br> <br> They have subsequently taken the same amount (in the region of R950) off my account via debit order THREE times. They sent me TEN emails in one day threatening legal action if my account was not paid as I had asked my bank to reverse the debit order. No amount of contact with with them has helped at all because one deals with a different operator each time you call, which in itself is a mission as you have to wait an age for your call to be answered. I am at my wits end and have no idea how to stop them from accessing my account.<br> <br> I will never again have any dealings with this company!