Problems with Stopping Impersonation and WCF

I have a WCF that I am creating for a system endpoint that I am looking to replace a webservice with.
I rquire that only a certain user be allowed to call the webservice so I send over the callers credentials when I call teh service like this
            System.ServiceModel.EndpointAddress end = new System.ServiceModel.EndpointAddress("net.tcp://ipddress:12000/SAMSVC/");
               
            wsealms.ServiceReference1.Service1Client myService = new wsealms.ServiceReference1.Service1Client();
            myService.ClientCredentials.Windows.ClientCredential = CredentialCache.DefaultCredentials as NetworkCredential;
            myService.Endpoi ...