XPages connect very poorly to all existing Domino design elements like script libraries (LotusScript and Java) and I'm afraid you cannot use Domino Web Service Consumer design element from SSJS directly (you need to start an agent to do that). I hope I'm wrong in this case but this lack of integration to anything we've developed in the past is a huge problem with XPages.
Anyway here is a way to call a web service with Apache Axis classes: