Vodacom
Data usage

I have a contract with Vodacom (cell no 072 213 6802) and on 25 June 2013 i was debited an amount of R1445.76 and when i log in to their website to check how possible is that i found out that there is a bill of R1038.32 and it says DATA USAGE, how could that be as i am on 120 off peak with BlackBerry Add-on BIS Free 24Mtns @R59.00 and also BlackBerry BIS @ R59.00 please someone do something this is a lot of money and i have never paid such a big amount before and i am not happy at all what is this data usage for

Cell 072 213 6802