Increase in Contract subscription

I Received an sms to inform me that my Smart Talk L Subscription will increase. My 24 month contract states that I should pay R399 per month for a 24 month period. Now they increasing this price without the contract period of 24 months being over. <br> <br> When I enquired about it, I was told that they have a clause in their terms and conditions allowing them to do so. <br> <br> What is the reason for a contract then if they can increase the contract price at any given time, with any given amount? and I just have to accept this price increase as I signed the contract for a 24 month period, and should I would like to cancel the contract a penalty will be payable. <br> <br> So they are forcing all their subscribers to this price increase. <br>