4,500 Rand that can't be explained

I have what I believed to be an unlimited (fair value) contract. This totalled almost 2,000 per month and has been consistent for a year - last month i was charged 7,000 - which apparently includes 4,500 for additional data. After emails with now response and 3 phone calls, the one today with a consultant who could not explain Jack Sh**t - i was eventually put through to Lungi a supervisor - she can't explain the additional 4,500 in data - she now tells me that i get 3 gigs of data during the day and 7 at night - i get a monthly SMS from Cell Ce and nowhere does it state this. I am also told that they charge 99 cents per meg - which would equate to 4.5 gigs of additional data - if this is so, then i will take legal action as nowhere did you tell me this - and you did not tell me that i had reached my limit - and these costs are excessive when your competitors charge nowhere near the same. I am promise that i would be called within 48 hours but i doubt that will happen. If you are taken by the CellC we will pay up to 10,000 - don't they make their money back some other way - A THOROUGHLY DISGUSTED CUSTOMER.