The SOAP API requires authentication, this requires either a username and password to be passed, or an Authentication Token.
A token can be generated with a process as discussed here:
getEEMCredentialsTokenForUser
Otherwise you will need to pass the username and password as you are showed:
<auth>
<user>itpamadmin</user>
<password>itpamdemo</password>
</auth>
You may want to look into use the REST API, which does allow you to pass the authentication in the header.
RESTful API Reference