No service no obligation to pay

I currently have a dispute with Mweb regarding cancellation of my contract with them, whereby Mweb Insists that I have to pay cancellation fee as I am liable and obligated to pay cell c being a 3rd party. What I am interested in is knowing why would I have to pay for a service that was never rendered and I have since asked Mweb to send me the communication in writing and also show me where in the contract that is stipulated. I have only received phone calls that mean absolutely nothing. I am now taking it upon myself to contact cell c to get that information, since I haven't used your service whatsoever. I will appreciate communication in writing as I am not prepared to pay for anyone for absolute no reason/service.