Working Nexmo Number Callback Change

gistfile1.txt

using System;
using System.Net;

public class HelloWorld
{
    static public void Main ()
    {
        string api_key = "xxxxx";
        string api_secret = "xxxxx";
        string country = "xx"; 
        string nexmo_number = "xxxxxxxxx";
        string callback_number = "xxxxxxxxxxx";
        
        Console.WriteLine("Attempting to change callback for number " + nexmo_number + " using..." );
        Console.WriteLine();
        Console.WriteLine("api_key = " + api_key);
        Console.WriteLine("api_secret = " + api_secret);
        Console.WriteLine("country = " + country);
        Console.WriteLine("callback_number = " + callback_number);
        Console.WriteLine();

        HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(
                                            "http://rest.nexmo.com/number/update/" + api_key 
                                            + "/" + api_secret + "/" + country + "/" + nexmo_number
                                            + "?voiceCallbackType=tel&voiceCallbackValue=" + callback_number );
        httpWebRequest.Method = "POST";
        httpWebRequest.ContentType = "application/x-www-form-urlencoded";
        HttpWebResponse httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();
        Console.WriteLine("Status " + httpResponse.StatusCode );
    }
}