I realize that only WebHttpBinding has this problem. To solve this problem, just add a behavior configuration in the client side configuration file like this:
<behaviors>
<endpointBehaviors>
<behavior name="webEndpoint">
<webHttp defaultBodyStyle="Wrapped"
defaultOutgoingResponseFormat="Xml"
helpEnabled="true"/>
</behavior>
</endpointBehaviors>
</behaviors>
Then, update the client endpoint to use the above endpoint behavior.
<client>
<endpoint binding="webHttpBinding"
bindingConfiguration="webHttp"
behaviorConfiguration="webEndpoint"
contract="ExpenseService.IExpenseService"
address="http://myservices/ExpenseService.svc">
</endpoint>
</client>
The problem should be solved.