web services use XML, so obviously with obj-c (or any other existent programming language) you can consume web server, but you need to parse "manually" the output and input. and send\receive with NSURLConnection (or ASIHTTPRequest).
There aren't library (that i know) that allow an easy integration as for java or .net.
But why not search on the forum?
http://www.iphonedevsdk.com/forum/ip...-via-soap.html
or at least google it!.