Increasing subscription!!!

Vodacom sends a casual mail to inform me that I will now have to pay R40 more a month on my contract... What happened to 24 month contract??? If I want to make any changes now such as downgrade or cancel, I will be fined, but they can do whatever they want!!!! And they don't even apply it to all contracts only the not so 'Smart' plans that I was forced to go onto as the talk 240 didn't 'exist' anymore.... Vodacom is disgusting!!!