Contract **********

I have a contract with vodacom for an iPad mini with an installment ofR305 every month, but for the month of January and February vodacom has been debbiting R750 from my account without any information why. When I call them they say I went over my one gig. Last year they told me that they had put a limit into my account so that I don't go overboard. This is not the first time vodacom takes my money **********ly. Last year I spent two months without data but they took my money still, this year they over charge me and it's becoming a habit. My contract ends in May 2016, this is their way of eating my money. If they put a limit into my account why do I pay R450 extra and why now when my contract is about to end, I'm tired of vodacom bad service and ***** they committed against me, I want my money back all R900.