Data contract changed, ***** my Data

I upgraded my Data contract this year, then after using it for 7 months Vodacom decided to take half of my data away, but I still pay the same. After escalating it half a dozen times they still say it was a system error.. So I request they listen to my phone call when I upgraded this contract, but they don't want to listen to that call..!!

I have the right as a consumer to expect that my phone call is my "contract" with them, since I haven't signed anything else... That phone call was recorded so it is my contract is it not?????

I am so sick and tired of dealing with Vodacom..