WCF web services have specific behaviour. It is possible to enable them to publish their WSDL description, see this article for some more details. See also this thread which gives more guidance and answers.
If you have published the WSDL it should be possible to import this definition in the Mendix Business Modeler, which enables you to create a visual mapping. However, it can depend on the specific service whether it is supported or not. We support all WS-I compliant WSDLs.