Soap return value

I’m using Xojo 2014r1 (but in previous version also) and using a soap call method i get this result(“Body”):
<ns1:callResponse xmlns:xsd=“http://www.w3.org/2001/XMLSchema” xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance” xmlns:SOAP-ENC=“http://schemas.xmlsoap.org/soap/encoding/” xmlns:ns2=“http://xml.apache.org/xml-soap” xmlns:ns1=“urn:Magento” xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”>product_id3215skuCAM01-39-BInameCAMICIA UOMO CLASSICA - 39-BIANCOset9typesimplecategory_ids

How can i read value of a particular field so as product_id?
When i use “xml.LoadXml(s)” where s is my xml returned by soap, it returns a null value.
Thanks for your help