It seems like there's missing a "ns1:" in front of arguments when parsing them.
E.g.
<iTrackingNumber xsi:type="xsd:string">17483</iTrackingNumber>
<sPassword xsi:type="xsd:string">FMDBPassword</sPassword>
<sUserName xsi:type="xsd:string">FMDBUser</sUserName>
Should be.
<ns1:iTrackingNumber xsi:type="xsd:string">17483</ns1:iTrackingNumber>
<ns1:sPassword xsi:type="xsd:string">FMDBPassword</ns1:sPassword>
<ns1:sUserName xsi:type="xsd:string">FMDBUser</ns1:sUserName>
I haven't looked into details for a more correct solution, but it helps in my case.
simple hack to show where it's missing