Access web service using Scott Klement's http_url_post_xml

This is the first time that I try to access a web-service using Scott
Klement's http_url_post_xml procedure:
Below is what my RPG code looks like:

myRC = http_url_post_xml(
myWebServiceURL
:%addr(mySoap) + 2
:%len(mySoap)
:*null
:%paddr(remUpdateRemedyWithUPSTrackingNumberResponse)
:%addr(myRemResponse)
:HTTP_TIMEOUT
:HTTP_USERAGENT
:'text/xml'
:myWebServiceSoapAction);

In debug, below are values for myWebServiceURL and
myWebServiceSoapAction:
myWebServiceURL =
http://devrem1/arsys/services/ARService?server=devrem1&webService=DalyUp
date
myWebServiceSoapAction = DalyUpdate/OpSet.

http_url_post_xml returns value of 500 upon completion of above
statement.

The URL for the WSDL document is at
http://devrem1/arsys/WSDL/public/devrem1/DalyUpdate
The service tag in the WSDL looks like below:
<service name="DalyUpdateService">
<port binding="s:DalyUpdateSoapBinding" name="DalyUpdateSoap">
<soap:address
location="http://devrem1/arsys/services/ARService?server=devrem1&webServ
ice=DalyUpdate" />
</port>
</service>


When I ask the web-service provider about http 500 error, she said that
I should post the request to the URL where the WDSL document is located
(http://devrem1/arsys/WSDL/public/devrem1/DalyUpdate). Is that right?
I thought I'm supposed to post to the URL indicated in the port tag of
the service tag.

Thanks