Problem in return value of webservicequery()

Hi All,

    I am able to call a webservice from "Call webservice" Node and get the expected result, but when I tried passing the same input parameters to the "webservicequery()" through an expression rule, I am getting the status code as 200 but the returnValue is null.

In Rule is below details are mentioned.

 " WSDL URL"  with "wsdlUrl"

  "Service" with "service"

 "Endpoint" with "port"

 "Operation" with "operation"

"HTTP Header" with "extensions"

Could someone please let me know what may be the issue causing this?

Thanks in advance!