this is an example of request to siebel web services with WSSOAP option turned on:
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
<SOAP-ENV:Header>
<ns:UsernameToken xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns="http://siebel.com/webservices" xmlns:ns0="http://schemas.xmlsoap.org/soap/envelope/">User name goes here</ns:UsernameToken>
<ns:PasswordText xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns="http://siebel.com/webservices" xmlns:ns0="http://schemas.xmlsoap.org/soap/envelope/">Password goes here</ns:PasswordText>
<ns:SessionType xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns="http://siebel.com/webservices" xmlns:ns0="http://schemas.xmlsoap.org/soap/envelope/">Session type goes here</ns:SessionType>
<ns:SessionToken xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns="http://siebel.com/webservices" xmlns:ns0="http://schemas.xmlsoap.org/soap/envelope/">Session token goes here</ns:SessionToken>
</SOAP-ENV:Header>
<SOAP-ENV:Body>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
without WSSOAP option you would have to either invoke that as anonymous user (configured on Siebel side) or put user name & password in URL.
Here you can find more information (Siebel Bookshelf): http://docs.oracle.com/cd/B40099_02/books/EAI2/EAI2_WebServices.html