Hello,
Can you give us a little more detail on what you are needing?
If you are referring to Dynamics Web services, then this is an econnect wrapper to GP. To hook into it, you would simply get the connection info from the web service into a service reference in Visual Studio, download the wsdl, and get your exposed classes for the service. Once you have this, you can send and retrieve data for which your credentials are set up for. There are examples available in the install for both c# and vb.net.
Here is a link to get you started: msdn.microsoft.com/.../cc534132.aspx
If you are referring to a custom web service that is not Dynamics GP web services, you can do what Ian suggests, capture the data, and do as you please with it.
As far as csv is concerned, you would expose the classes for the service, and map your csv data to a collection of whatever object you are sending to GP. Web services inherently use either xml (SOAP) or json (javascript notation) depending how new the service is built.