RMCS REFUSE TO CANCEL A CONTRACT

Last year I received an sms telling me to subscribe for airtime at discounted price every month for 6 months. It was not stated as my numbers will be changed from prepaid to contract, I was not satisfied at all as my number was changed from prepaid to contract without a verbal consent despite the reply to the sms. I have been calling RMCS since last year trying to cancel this contract with no luck I'm being promised a call back from a cancelation department but I never receive a call. Even today no one ever got back to me to cancel this contract. 6 months have long past and this thing still continues, I no longer use my Jet account where they deduct. Please help I really want to cancel but don't know what to do now. Even on monday I called, they promised to get back to me within 48 hrs for cancelation, even today I'm still waiting.