Bad customer service from vodacom

I had a bad experience with vodacom Nelson Mandela At Sandton I opened a contract and was on open line without me being aware of tht and made me sign without me reading the contract now am paying what was not agreed to be paid am paying more and when I call them they do not assist and give bad customer service, at this point I want to cancel the contract and move on I don't even have three months with them but they treat me like trash and they don't appreciate my money.