How to call/invoke webservice method Using WSDL file as ref?

I am not able to invoke the Web service Method using WSDL web reffernce.

Step I Follow to invoke the webservice method

1. Add Web refernce of WSDL file. (It generates the refernce method )

2. create instance of service.

3. assign parameter to service method.

Sample c# code

CM_PORTG3_Ref.CM_PORTG3 _CM_PORTG3 = new CM_PORTG3_Ref.CM_PORTG3();
_CM_PORTG3.startdate = "1-Aug-2015";
_CM_PORTG3.enddate = "31-Aug-2015";
_CM_PORTG3.aid = "Agent1";

CM_PORTG3_Ref.CM_PORTG3Service _CM_PORTG3Service = new CM_PORTG3_Ref.CM_PORTG3Service();

////Smaple WSDl file attached