Vodacom recommends package change then overcharges

2 months ago, I got a phone call from Vodacom recommending I change my contract package to a Smart L to save money. They convinced me and everything went OK till I got my latest bill. After investigation I found that on 22 Jan 2015 I used 2 Gigs of data and was charged a whopping R1400+Vat for this.The same 2 gigs that when bought as a bundle will cost R300. I contacted Vodacom to change my contract as this is completely unacceptable. I was told that I could convert to a smart L top up where out of bundle rates do not apply, which I have done. I demand Vodacom refund me the +- 1711.40 for out of bundle data charges at 85c per meg (which is ********) after Vodacom incorrectly advised me to change to the wrong contract package. TCF gone wrong!