event not firing in web service

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C#

ASP.NET

Hello all.I have an issue with firing event in web service.am using the mCore™ SMS to test ussd input in my service.In windows form application,when i check the checkbox to fire new incoming ussd,its working okay.but the problem is in a web service,I have created a function on start which i connect with modem and that works okay.The problem is the the event which receives the ussd request,its not firing at all .Here is my code.

public void <pre lang="cs">objSMS_NewUSSDReceived(object sender, mCore.NewUSSDReceivedEventArgs e)
       {
           string message = e.Message.ToString();
           string status = e.Status.ToString();


           if (message.Contains("Welcome user"))
           {
                 //MY FUNCTION TO CALL

           }
           else
           {

               //problem with ussd



           }
       }

When the service starts on debug,i call the function below which has the ussd request.However it does not trigger any event

  public void Test()
        {
            bool result = objSMS.SendUSSD("*1234#");
            if (result)
            {
            
                //it lands in this code below but nothen happens.The event "objSMS_NewUSSDReceived" is not triggered

                objSMS.NewUSSDReceived +=objSMS_NewUSSDReceived;
                objSMS.NewUSSDIndication = true;


            }