No signal by cell c in my area

I told the sales person that I don't want cell c because of poor signal/service in Middelburg MP. He said the problem was sorted out and I would not have poor service. When someone phones I can't hear them keeps on braking up, at night and day the data signal goes away for hours. Why should keep on paying for this service I'm not getting at all?? I want this contract terminated because they are not bring there part of the contract, the simcard have not been in use for months now. The person who phoned for the contract was recorded and he stated the signal wil work perfect