Cannot stop Multichoice billing my old account

We wanted to change our direct debit details from one bank account to another. We called and emailed Multichoice with the new details (along with all of our other suppliers) and Mutlichoice billed the same account. None of our other suppliers did. We called in an explained what they had done, they said the matter had now been resolved and again they billed the same account. I went onto their self service portal, changed my payment details to my credit card but couldn't cancel the direct debit so rung in and again asked them to cancel the direct debit, they said they would. Again they again attempted to bill the old account AND they billed my credit card. I rung in and asked for a manager and explained the situation. He said he would escalate the matter so I emailed my details and one month later, they attempted to bill the old account. I then went onto their website to log a complaint and haven't heard anything back. Can anyone help please?