Incorrect billing

I have logged several calls with altec autopage but with no joy. I have subscribed to data bundle of 2 gigs per month but on second day of use it shows i have less than 500 mb left for the month. I probably search the internet or download for an hour max. I've contacted them to complain that the data charges are incorrect and results into huge amounts being debitted from my account. I have asked them to investigate but with no joy. Absolutely bad service. The billing calculations needs auditing.