Increase package prices during contract as they want

I signed up for a 24 month contract at a certain rate and then 5 or 6 months in, they increase the package price and say in the terms and conditions of the contract they state they have the right to change prices. Why do we sign a 24 month contract then.

And their suggestion is downgrade your package and get fewer minutes that will suit your pocket. absolute bull! I signed up for this promotion and now I must suffer.