Vodacom stealing DATA

Having been on contract for a year with vodacom, i never called in and complain about anyhting, as i use my data responsibly and at all times KNOW Exactly how much data i have left. The other night, i check my data balance and it said i have 400mb left, then as i went to google it tells me i have run out of data, to my complete disbelief i quickly do the vodacom balance check again, and low and behold it tells me i have ZERO mb left, how can my data jump from 400mb to ZERO in a few seconds when there is no downloads, no background downloads or updates going on ? ! !

And yes i know all operating systems inside out as i am a qualified MCSE Technician

So for the very first time i call them up after never complianing about anything and ask them to sort the problem out for me, what do i get in return ?? A slap in the face, telling me no it's my pc that used up the data ??? .....What the ???

I have NOTHING running in the background, ALL updates are turned off, no traffic was registered in my data monitor, it has NEVER happened, this whole year that i was using the internet, Now they want to tell ME i should check if these basic idiotic things is turned off, for crying out loud i can tell THEM what additional things they can tell their CLIENTS to turn off, i even use an OFFLINE toggle on my browser cancelling all traffic instantly.

Does anyone know how i can get my data back ?