overcharged for my monthly debit

I am getting tired of Vodacom, this month they charged me 604 on a contract of 208. I don't know how they came to that amount, but this is really frustrating. I have been on vodacom for a month and have been trying to cancel my contract. This is absolutely ridiculous, my bank charges are to much because of this .This is my second complaint in one month. I don't know what must be done for them to take my things seriously. I want my money bank and to leave this contract, I was better off with cellc.