Paying for something I cant verify

I have a data contract with vodacom that has been on a 2gig contract for over 19 months. I have paid R99 a month R this entire time. In January and February I got bills in excess of R1000. I queried it and asked for proof of where this data was being used as I havent done anything differently. No physical proof was given. I shut off all my applications and web browser from using data and I still got a bill for approx R600. Vodacom are charging me exhibitant rates, I have gotten no proof of why. I have paid timeously but feel I'm being wrongfully billed. I have migrated since. I require proof of where this data was used and I ask why I wasn't alerted when my data bundle was about to run out and out of bundle rates would apply. Being charged R2 per Meg is something clients should be warned of by an alert as I have experienced with my other service providers. Sorely disasapointed in vodacom.