Vodacom mobile data

Well Vodacom....I'm starting to wonder, where'd my data go??? I have Wi-Fi at home and Wi-Fi at work. It's nearly impossible to deplete 684MB while driving to and from work!!! I do NOT and I want to reiterate, I do NOT use my phone at all while driving, I'm old school, whatever it is, it can wait until I get home or to work. Why do you ***** my data, who do you credit it to?? It's not enough that you pin us down with a 3 year contract and keep increasing rates in those 3 years, but you help yourself to our data too!!!??? Disgrace is what it is. Especially being a customer for 20 years and giving the benefit of the doubt. You disappoint dismally.