That's how I tried to do it at the start though. But nothing happens when I click the button.
Well at the bottom of the page I get this: Unable to find matching navigation case with from-view-id '/contactUs.xhtml' for action '/SOAPServlet' with outcome '/SOAPServlet'
What you are trying to attempt will not work. The moment you start using JSF tags / components, any reference to a bean or object, JSF tries to look within its context, facesconfig. It does not go outside its perimeter.
If your intention is to all call a servlet by clicking a link within a page rendered by JSF, use regualr HTML tags or call a managed bean and then forward to a servlet