Increase

I currently have 2 contracts with Vodacom, I received price increase notification. I have never seen such a nonsense in my life, I have just taken these contracts out in December and already you want to increase. I have have never experience such a load of bullsh..! All my contracts are for 24 months with a fixed amounts, I don't remember signing for variable amounts.Surely this is breach of contract. Whats the point of signing a contact with fixed amount and then you just have the right to increase it?