The remote name could not be resolved: 'staging.www.wwalliance.com'

<system.net>
      <defaultProxy enabled="true" useDefaultCredentials="true">
      <proxy usesystemdefault="True"/>  
    </defaultProxy>
  </system.net>

string   CallOriginMethod()  
           {                       
                string uri = "http://staging.www.wwalliance.com/webservice/rest/globalrateorigin/origin.xml?";
          
                string Method = "POST";
            HttpWebRequest req = WebRequest.Create(uri) as HttpWebRequest;
            req.KeepAlive = false;
            req.Method = Method.ToUpper();

            if (("POST,PUT").Split(',').Contains(Method.ToUpper()))
            {

                string stringxml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
   " <GlobalrateoriginRequest xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:noNamespaceSchemaLocation=\"WWA_Rate_Lookup_origins_request_version_2.0.1.xsd\">" +
  "<GlobalrateoriginEnvelope><SenderID>test_agility</SenderID><ReceiverID>restapi</ReceiverID><Password>01870fa4b08a1</Password><Type>Globalrate_Origin_Request</Type> " +
     "<Version>2.0.1</Version><EnvelopeID>123</EnvelopeID></GlobalrateoriginEnvelope><GlobalrateoriginRequestDetails><Date>2013-04-25</Date><Customeralias>AGILITY</Customeralias>" +
   "</GlobalrateoriginRequestDetails></GlobalrateoriginRequest>"; 
             
                byte[] buffer = Encoding.ASCII.GetBytes(stringxml);
                
                req.ContentLength = buffer.Length;
                req.ContentType = "text/xml";
                Stream PostData = req.GetRequestStream();
                PostData.Write(buffer, 0, buffer.Length);
                PostData.Close();
              
            }
               // declare & read response from service
            HttpWebResponse resp = req.GetResponse() as HttpWebResponse;
               // set utf8 encoding       
               Encoding enc = System.Text.Encoding.GetEncoding(1252);     
                   // read response stream from response object    
               StreamReader loResponseStream = new StreamReader
                   (resp.GetResponseStream(), enc);
               String strResult = string.Empty;
               // read string from stream data    
               strResult = loResponseStream.ReadToEnd();      
               // close the stream object    
               loResponseStream.Close();     
               // close the response object   
               resp.Close();
               return strResult;
           }

var docs = XElement.Parse(CallOriginMethod());