Is the SOAP stack you're using compatible with JME? I would imagine that you need to rewrite the client to use the classes in javax.microedition.io instead of the java.net classes (which don't exist in JME).
The key is, by creating Web services client using NetBeans feature, and then use the class XXX_stub.class to create object, and then call the object method. The XXX will be a specific Web services name.
Using NetBeans to call a web services in J2ME is as easy as calling local method.