Subscription Increase

Looked at my February invoice, and realised that my subscription has been increased. I phone the 140 customer care, and was advised that their subscription increased to all Cell C users. They even told me that they did sent me a SMS. Well Cell C, in September 2013, I signed a CONTRACT for 24 MONTHS for R399, I did not sign that my rates will increase 18 months later and you did not inform me that the rates would increase in that very same contract, otherwise I would have spent my money somewhere else! I want a refund or I will take my contract somewhere else! Lastly, you can't inform the client during his contract (which I did sign for 24 months) that the rates will increase, common decency would be to increase the rates after the 24 months, when the contract is at its end, notify the client if he/she would like to continue for the next 24 months! Is this the way you treat a customer that used your services for 12 years?