This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
You may want to have a look at the @SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE) annotation, that enable you to set a parameter style.
I am not entirely sure that this will give you the desired result, but give it a try and let us know!
If you are doing WSDL-first development, then there should be a way to specify the parameter style through a JAXB binding file.