Configuration of Class Library

I have developed a ws client in a class library and the code of the ws client is generated by adding a web references.  When I want to move the ws client from uat environment to production environment, the client does not work at all. The problem is raised since I only update the configuration of app.config  inside the class library. As the ws client is a class library, the configuration in app.config will be ignored. Afterwards, I update the  Reference.cs which is generated by vs.