Execessive data charges

After the upgrade the account was normal and all of a sudden from December 2014 I received huge accounts relating to data usage. We use the Ipad and laptop for internet usage. The phone is only used to alert us of incoming e-mails. I bought an additional 1Gig data bundle, but that did not help either. On 18 April the local Vodashop showed me that there was already a data charge on my account despite the fact that there was still 1.2Gig data left for the month. The itemised billing only reflects \internet"- we don't know which sites were accessed. I suspect that I am charged incorrectly - may be a Vodacom software issue. The charge once you exceed your data bundle is ridiculous - R2000 per 1Gig. Not sure how Vodacom justifies this rate."""