Price increase

I received SMSs stating my contracts will be increased on 1 May and they have not expired yet. When I renewed my contracts I signed that I would pay a set amount for 24 months. No matter what the Ts and Cs state, this is breach of contract. Or at least false advertising. I have 3 contracts with Vodacom and if they insist on increasing my monthly payments I will end all 3! I sent 2 queries but got no reply. So on top of this issue their client service is also non existent.