Vodacom *******

I received a call from one of Vodacoms sales agent advising that I can get more minutes and data on my current plan and I did not need to pay more infact this new price plan will be much less with more benefits. I asked him several times if he was sure that I will not be paying more, he assured me that I will not be paying more and that if I'm unhappy with the new price plan I can change back to my old one. I agreed to the change, now I have just received my invoice and it shows that I will be paying double then what I used to pay! I called the call center and they changed my plan however they confirmed that I will have to pay the amount as per my invoice. I was **** into believing I would be paying less so why am I being punished for something I didn't agree to? Vodacom has been doing this to their contract customers and I cant wait for my contract to end so that I never take another contract with them! They are ****s and *******!