Price hike during a 2-year contract?

Yesterday I, and many others (as per social media comments received) received an sms from Vodacom informing me that my subscription on my now 14-month old 2-year contract with them, will be increased by +-11% on 1st May 2015! When I called Vodacom yesterday querying how they can do this, all I was told by the consultant on the line was that there is a clause in the contract that states that they can in fact do this! I wonder if the people selling the contracts to the public are even aware of such a 'clause', as I certainly was NOT informed of this clause upon signing up in February 2014!<br> <br> I would think that, according to responses received on my post on social media, that Vodacom are simply inviting a mass exodus from their contract members. I for one, will certainly be going back to my original provider MTN. In all the years I was with MTN, I NEVER experienced this type of disregard of a signed and agreed-upon contract premium/subscription!<br> Liz