Increase of subscription

I received the following SMS: From 1st of May 2015 your uChoose 100 subscription will increase from R99 - R110 per month.Your new price plan is uChoose 110. I signed a contract for 24 months, then surely it must be ******* to increase the subscription in the middle of the contract period! If they can do this from their side then maybe I can cancel my contract with them and go over to another company