Vodacom not honoring new deal

Dear Vodacom, I got an sms from you informing me that you plan to change the pricing on my contracts. One specific contract I was going to cancel last year and port to another network because I needed more minutes for less money. You then came back to me with a good deal to retain my business and keep me on your network. This contract is now almost doubling in price. That is ********* no matter what you contracts say. I expect this deal to be honored based on the fact that it’s less than 3 months old! I’ve been a loyal customer for over 20 years and I spent a load of money with you every month. Could someone kindly get back to me.