Incorrect Billing for 4 months

I bought a new Explora on the special that Multichoice had and ever since then i have had endless problems with them debiting my account. The first time they too off triple the subscription fee and it took them a month to refund me and a promise that this was sorted out. Incorrect debit order went off again. After the second time i asked them to cancel my debit order as i can not have incorrect amount of money keep going off my account when i need that money for other debit orders. They agreed to this but guess what, even though i am paying them by EFT now they still debiting my account after more promises that this has been sorted out. This has happened 4 times now. How can a company that is so big and has such advanced technology not get my account right. This is so frustrating and time consuming. I can not believe how useless and *********** Multichoice accounts department are.