XML Example for XServices (v17)

Hello,

I have been tasked with creating a Proof of Concept application that interfaces with XServices via XML. I have read the Services guide, I have gone over the WDSL and the XSD, and have created a simple XML to get an item, using the getItemById and am attempting to test the XML via Postman. However, no matter how I tweak the XML or the HTTP Parameters, I get back a HTTP 500 response, Invalid Message.

I have attached my current iteration for the XML, GetItemById.txt

I am assuming that there is something wrong with the XML, but I cannot see it. Any assistance would be appreciated.