Vodacom - Misinformation by telesales person

A while ago, possibly a month or six weeks ago, I was contacted by a Vodacom agent regarding the renewal of my cel phone contracts. Two of the items discussed was the cost and new hand sets. I repeated several times that I did not want a significant increase in the monthly cost of the contract and that I did not require a new handsets. The agent insisted that the new handsets were a bonus and that would not impact my monthly payment.
Today, when I checked my Vodacom statement and the invoices I see that my one invoice is significantly higher than before and that there is a charge for a handset albeit only R20-00. This is not what I agreed with the agent. I still have the two handsets I recieved in the boxes. As I explained to the agent I do not need them.