Cell C Illigally increases your subscription

Cell C sent me a statement which shows that both my contracts with them are increased per month. They have no right to increase the cellphone subscription as it is a contract and is binding for 24 months. They dictate to the customer what he or she is forced to pay - this is ******* under our consumer protection act. The subscription is binding for 24 months therefore who are they to increase it as they like, I refuse to pay more than what was agreed on by me with them months ago, the issue is where is my choice in this as a consumer?<br> They are also not assisting em with any feedback, they just call and dictate what you must pay! its outrageous and I refuse to pay even a R1 more. I would like to know where I signed that I will pay more than R99 per month and R50 per month subscription on my contracts, they have to provide me with the contract clause which states that I agree to pay more? they cant therefore they cant bill any of us more than what we agreed for them to bill us in terms of our subscriptions, calls are another matter!