Incorrect billing

I had a account for data with autopage. And my contract has been an average R700 per month and in july i was billed R3500 and i am just told its gprs. I called to enquire and i was given a reference number and investigated but it came to no avail. I was billed for data i did not use fr R2000 and my itemised billing does not show such from my side and callin in the consumer centre did not help me. How can i use R2000 of data wen i hv 2gigs a month and i bought an extra 500megs. There is no proof of such in my statements yet my money is gone. Worst service possible and no 1 has a clear explanation. R2000 is a lot to loose on data i did not use nd there is not one to help with the customer services. I am mad as hell and i wil never renew my subscription with autopage and i wil never recoment anyone for such poor services.