Vodacom contract price increase

I got an SMS saying that Vodacom will be increasing my data allocation and pricing on my current contract from 1 May 2018. I phoned Vodacom about this problem I had as I did not want my contract to change. I already had a free data bundle from Voadcom due to the poor customer service and irritation I was caused when I updated my contract a year ago.

I was told it was part of the T's and C's but I have a problem with this as I got this contract at a specified price and now it has changed within the 24 months I signed for.

Please can someone contact me to provide a solution to this.