You are probably passing the service a message that is not valid. You should have a look at the WSDL; there should be one or more schemas or schema documents listed inside it. Those will tell you how you can construct the body of the SOAP message.
I was experiencing your problem before when i develop the code as similar you given.Check your again WSDL file and you need to request a single SOAP message in the single class otherwise your methods(given in first part) of your question will be clash. Please go to the following link, i hope it will help you, 1)kosmaczewski.net 2)http://icodeblog.com/2008/11/03/iphone-programming-tutorial-intro-to-soap-web-services/ 3)http://viium.com