Exception while sending sms throgh mashup.com api with site2sms

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C#

ASP.NET

SMS

Exception while sending sms throgh mashup.com api with site2sms username,password,.Mashupkey everything is right but exception occuring

<pre lang="text">

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
using System.Net;
using System.IO;
using ASPSnippets.SmsAPI;

protected void Button_SendSms_Click(object sender, EventArgs e)
{
SMS.APIType = SMSGateway.Site2SMS;
SMS.MashapeKey = "Mashupkey";
SMS.Username = TextBox_UserName.Text.Trim();
SMS.Password = TextBox_Password.Text.Trim();
if (TextBox_SendTo.Text.Trim().IndexOf(",") == -1)
{
//Single SMS
SMS.SendSms(TextBox_ReceiptNumber.Text.Trim(),TextBox_Message.Text.Trim());
}
else
{
////Multiple SMS
List<string> numbers = TextBox_ReceiptNumber.Trim().Split(',').ToList();
SMS.SendSms(numbers, TextBox_Message.Text.Trim());
}
}

build Successfully After runing and clicking on button following error Occurred 
 popup on //single sms 
An exception of type 'System.Exception' occurred in ASPSnippets.SmsAPI.dll but was not handled in user code

Additional information: {"response":"This API is Deprecated due to take down request from site2sms."}