First time user fault problem

Sorry if this is dumb. I am a beginner.

I have a simple test service in Visual Studio 2010 that works fine with the built in WCF Test Client.

I can get the wsdl for the service and create a new project in soapUI. The simple methods in this test project are exposed correctly and requests is created.

I send the request but get an error. The service is running, it didn't need credentials to get the wsdl so i am confused over what is missing to be able to use soapUI like this. I think it must be something to do with the tempuri.org namespace or similar. Can anyone point me gently in the right direction?

Here is the request:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:tem="http://tempuri.org/">
   <soap:Header/>
   <soap:Body>
      <tem:GetEvals/>
   </soap:Body>
</soap:Envelope>

...and here is the fault response:

<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing">
   <s:Header>
      <a:Action s:mustUnderstand="1">http://www.w3.org/2005/08/addressing/soap/fault</a:Action>
   </s:Header>
   <s:Body>
      <s:Fault>
         <s:Code>
            <s:Value>s:Sender</s:Value>
            <s:Subcode>
               <s:Value xmlns:a="http://schemas.xmlsoap.org/ws/2005/02/sc">a:BadContextToken</s:Value>
            </s:Subcode>
         </s:Code>
         <s:Reason>
            <s:Text xml:lang="en-US">The message could not be processed. This is most likely because the action 'http://tempuri.org/IEvalService/GetEvals' is incorrect or because the message contains an invalid or expired security context token or because there is a mismatch between bindings. The security context token would be invalid if the service aborted the channel due to inactivity. To prevent the service from aborting idle sessions prematurely increase the Receive timeout on the service endpoint's binding.</s:Text>
         </s:Reason>
      </s:Fault>
   </s:Body>
</s:Envelope>