Data charges.. crazy

Vodacom have without notification of balance.. gone ahead and charged me exorbitant amounts for data that was not used.. I have a gig allocated and I still add on data from my bank when I get notified.. now all of a sudden I'm sitting with 2 months billing of over 2500 when I should be only paying 600.. what the eff vodacom? As usual you never fail to surprise. Log a call.. wait 2 days for confirmation of said enquiry.. then need to wait a further 7 days for resolution.. which will probably be incorrect.. vodacom you never wait a second to take money out of my account.. and now this? I can't afford 2 months of 2500 ****ing cellphone bill.. fix this