How do you consume it? In case you created an app.config for your webpart, that won't work as web part are executed in the context of the w3wp.exe process.
You have to either manually setup the endpoints in your Service Client, or put it in the web.config of the Sharepoint Virtual Directory (c:\inetpub\wwwroot\wss\80 I think). If you have multiple servers, add it to all. (I would recommend creating a feature receiver that modifies the web.config, but I learned the hard way that SPWebConfigModification should never ever be used)
Programmatically setting up the Client:
var endpoint = new EndpointAddress(new Uri("http://your/wcf/endpoint"));
var binding = new WSHttpBinding();
var client = new YourWCFClient(binding, endpoint);
The exact binding depends on your configuration of course - WCF is a bit tricky here, but if you have a working client already, check it's app.config for the binding info and MSDN for the classes that derive from System.ServiceModel.Channels.Binding to find the correct one.