WebException The operation has timed out after 100 seconds C#

Question

I am having an issue in calling specific WS's when the response takes longer than 100 seconds to be generated.

Following my code:

try {
    XmlDocument soapEnvelopeXml = CreateSoapEnvelope(request);
    HttpWebRequest webRequest = CreateWebRequest(url, action, username, password);
    webRequest.ContinueTimeout = 200000;
    webRequest.ReadWriteTimeout = 200000;
    InsertSoapEnvelopeIntoWebRequest(soapEnvelopeXml, webRequest);  
    // begin async call to web request.
    IAsyncResult asyncResult = webRequest.BeginGetResponse(null, null);

    // suspend this thread until call is complete. You might want to        
      if( asyncResult.AsyncWaitHandle.WaitOne(-1) )
        {
            //MessageBox.Show("Call completed!!!");
            // get the response from the completed web request.
            string soapResult;
            using (WebResponse webResponse = webRequest.EndGetResponse(asyncResult))
                {           
                    using (StreamReader rd = new StreamReader(webResponse.GetResponseStream()))
                    {
                        soapResult = rd.ReadToEnd();
                    }
                    response = soapResult;
                    success = true;
                    errMessage = "";
                }
        }
          else
                {
                    MessageBox.Show( "Call didn't complete in 180 seconds" );
                    errMessage = "Call didn't complete in 180 seconds";
                    throw new Exception(errMessage);
                }       
}
  catch(Exception ex) {
            errMessage = ex.GetType().Name + " " + ex.Message;
            success = false;
            response = "";            
        }

I tried several suggested ways to set a proper timeout, but unfortunately no success. Can you please help me in solving this issue?