Not disclosing all information telephonically

I was busy cancelling my cellphone contract after years with Vodacom. However, Vodacom now has a retention department to try and avoid customers from going to other service providers. So, they asked the reason for me leaving and I explained that Telkom had cheaper packages for the same product and more data. The lady then negotiated then a better deal for me. She basically suggested to down grade my current package to the smart standard S, and to include extra 100 minutes vodacom to vodacom and 500mb extra @ a total monthly payment of R469 per month. I explicitly asked her if this was the total cost and if there are any hidden cost. She said no, she said she will even give me CLIP and itemised billing for free at no charge. However, after i telephonically excepted the deal, I received an email quotation reflecting amonts that was not disclosed to me. When I enquired about this a second person said that the quote was wrong. Now Vodacom expects me to pay an once amount of R498 to them which was I was never informed about, I struggle to get hild of anyone to assist me from Vodacom, I left numerous messages, promises were made to phone me but knowone from Vodacom contacted me!!