Contract price hike

Hi. I have been a cell C customer ever since I took out a cellphone contract. Currently I am on the R400 pm contract which includes 400 minutes etc. As of February this year, I noticed an increase in my monthly bill. . When i made an inquiry at the Cell C store at Liberty Midlands Mall in KZN, I was told that my contract price had increased and that it was part of the terms and conditions that Cell C can increase the monthly price of my contract as per their leisure. I was also now being charged for itemised billing which I do not receive. When I initially took out the contract, I signed and agreed to pay R400 pm. That was the terms of the contract. I feel it is un-constitutional to have such terms which allow Cell C to increase my monthly rate. This also goes against their TV advert which encourages people to transfer to Cell C when their service provider increases their monthly rates. (Cell C claims to not have increased rates). Also, if I want to cancel the contract, there are penalties. The mobile number is provided and account can be accessed using the number.