mobile phone contract

[Markp13]

I'm not sure if this is the right place for this question but here goes;

I have just got a letter saying the price of the monthly payments of my mobile contract is going up. Am I right in saying that I can now cancel that contract as they have changed the terms?

I thought I seen something on the news lately saying I could as the small print in their contracts saying I couldn't is illegal.

anyone?