charge me for data which I did n't use

On January 13, 2015, I went to voda shop to renew my weekender 120 contract, I found that vodacom is no more offer that contract, then I migrated to 2 gig top up, and they told me I will get data on February. On February they loaded 2 gig of data as they promise, few days after they sent high bill for me to pay, when I enquire about it they told me my tablet was on auto update which was not true and they promise to take it to auditors after few days they sent a massage to my phone to tell me that the case was closed without telling me what happened. Vodacom used advantage that my line was open line with no limit and they charge me what they like and they load **** settings on my tab and expecting me to pay for their ****s. I refused to pay for what I did n't use, I am waiting for them to close my line because they do what ever they like to increase pockets and share price and destroying our credit record. Vodacom must be transparent.