var url = "https://txnhog.co/txn/api/your_message_key";
var httpRequest = (HttpWebRequest)WebRequest.Create(url);
httpRequest.Method = "POST";
httpRequest.ContentType = "application/x-www-form-urlencoded";
var data = "apiKey=sdkrjwhaldkgh3pwdfohawp4lyu&name=Shawn%20Spencer&phone=2085559988";
using (var streamWriter = new StreamWriter(httpRequest.GetRequestStream()))
streamWriter.Write(data);
var httpResponse = (HttpWebResponse)httpRequest.GetResponse();
using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
var result = streamReader.ReadToEnd();
Console.WriteLine(httpResponse.StatusCode);