How to return last node having namespace in it using Xquery

I have this file, which have namespaces in it, I am trying to write a Xquery which will return, the last node having the namespace, but unabe to find the logic to return the namespace node(PS: I am new to Xquery)

XML File -

<XML>
  <SOAPMessage>
    <soapenv:Envelope   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
      <soapenv:Body>
        <postRequestResponse    xmlns="http://company.com">
          <postRequestReturn>
            <OnlineBRE  xmlns="">
              <Proccode>NUM</Proccode>
            </OnlineBRE>
          </postRequestReturn>
        </postRequestResponse>
      </soapenv:Body>
    </soapenv:Envelope>
  </SOAPMessage>
</XML>

  

I have tried a query to return node with exact string value, but that didn't work.

Based on your comments on the Mads Hansen's answer I came up with this:

declare namespace array = "http://www.w3.org/2005/xpath-functions/array";

declare function local:ns-changed ($current as element(), $last-ns, $last-element) {
  $current/element() ! (
    let $child-ns := namespace-uri-from-QName(node-name(.))
    return
      if ( $child-ns = $last-ns )
      then local:ns-changed(., $last-ns, $last-element)
      else local:ns-changed(., $child-ns, .)
  ),
  $last-element
};

let $root :=
<XML>
  <SOAPMessage>
    <soapenv:Envelope   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
      <soapenv:Body>
        <postRequestResponse    xmlns="http://company.com">
          <postRequestReturn>
            <OnlineBRE  xmlns="">
              <Proccode>NUM</Proccode>
            </OnlineBRE>
          </postRequestReturn>
        </postRequestResponse>
      </soapenv:Body>
    </soapenv:Envelope>
  </SOAPMessage>
</XML>

let $initial-ns := namespace-uri-from-QName(node-name($root))
let $wanted := head(local:ns-changed($root, $initial-ns, $root))

return $wanted

I may not be pretty and inefficient and also only tested on your provided input, but it does what you want.

Here you can see it in action https://xqueryfiddle.liberty-development.net/3Nzd8c9/1

Currently it returns the last element where the namespace changed. To return the node-name or the value or something else modify the last line.