Penalty for contract with proof of contract

I bought a new vehicle in around May this year the insurance company required a tracking device installed on the vehicle. My wife had a matrix device on her vehicle which we had traded so she canceled with them and I contacted them to install the beame on my new car all this was on the phone. I told them that to install the device knowing that its a month to month contract. Today when I called them which is a mission to get hold of the customer Care . I told the consultant I want to cancel the contract , the consultant said since I have a 36 month contract I would have to pay a penalty of R 900 if I want to cancel, I then asked the consultant to show me proof of the contract which she rep**** its a voice recording contract. I asked for proof of that but she said she don't have excess to that. My submision: There was clearly no consensus between Matrix and myself about a 36 month contract. The contract is not in writing. They are not willing to supply proof of the recording. If they want to charge me a penalty of R900 I am willing to go to court to challenge the validity of the contract because clearly there was a misrepresentation of the product.