Vodacom does as they want with your account and you have to pay

I got an SMS saying that my data was up. I went online to purchase recurring data of 2gig per month and found that Vodacom added 6GB data for 7 days to my account without my permission. They say that I put it on, but I would surely have known and why would I go online to put Data on if I have already done it? They are charging me an arm and a leg for something I do not need and did not buy! Vodacom this will be my last contract with you! I have been a customer for over 15 years, but will be moving over to a different network after this. Corporate *******! Milking their customer and *****ing. I can't afford this! Who in the world uses 6 freaking gigs in 7 days? What am I? A streaming service? I called in and was told that they can't give me a reference number for my enquiry. Now this was not the help person's fault, but clearly Vodacom's system is set up to ***** and designed that you can't query the problem. What a farce.