Why do I receive an "Operation Not Found..." error when I send a soap message to the Chat UQ API?

Environment:

Chat API

Issue:

When I send this request:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:v1="urn:messages.uq.chat.ws.rightnow.com/v1_1">
<soapenv:Header>
        <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" mustUnderstand="1">
            <wsse:UsernameToken>
                <wsse:Username>username</wsse:Username>
                <wsse:Password Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText">xxxxx</wsse:Password>
            </wsse:UsernameToken>
        </wsse:Security>
    </soapenv:Header>
    <soapenv:Body>
      <v1:Authentication>
         <v1:TransactionRequestData>
            <v1:Timestamp>2015-09-28T21:49:45</v1:Timestamp>
            <v1:TransactionID>1</v1:TransactionID>
            <v1:SiteName>yoursite</v1:SiteName>
         </v1:TransactionRequestData>
      </v1:Authentication>
   </soapenv:Body>
</soapenv:Envelope>

To this end point:

https://<my site>.custhelp.com/cgi-bin/<my interface>.cfg/services/chat_soap

I get this response:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Body>
      <soapenv:Fault>
         <faultcode>soapenv:Server</faultcode>
         <faultstring>Operation Not Found</faultstring>
         <detail>
            <Exception>Operation Not Found, Endpoint reference address is http://<yoursite>.custhelp.com:80/cgi-bin/<your interface>.cfg/services/chat_soap and wsa actions is (null)</Exception>
         </detail>
      </soapenv:Fault>
   </soapenv:Body>
</soapenv:Envelope>

What does this error mean? 

Resolution:

This means you are sending to the wrong endpoint.  Check to be sure that you are using the ChatURL returned by getChatURL operation.