Signed a contract but price increases

Hi, I signed a 24 month contract in which I pay R299 for Smart M.... How do you now have the right to just increase my monthly fee but still bind me to the contract... you could have doubled it if you wanted to and I would still be binded to my 24 months agreement.... this is poor business practice! <br> I sent an email to your customer service mailbox and never got a reply. How impolite can you be.