Excessive data usage

I have had my contract with vodacom for over 4 years now and multiple accounts. Thus morning I saw a debit order go through for the amount of R6011. Upon further investigation from my side I saw they charged me almost R4000 for data usage, my data bundle has never been depleted (in the last 4 years), as my phone is permanently connected to wifi (home and work), and if not I have a 2gb bundle, once I receive a msg from vodacom that says my data is nearing depletion I also buy additional bundles so this is not possible. <br> <br> Vodacom please fix the issue asap! Otherwise I will cancel all my contracts, and take the matter further.