SMS not deliver on a perticular mobile .. but code get successfully executed

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using SMSClientLib;
using System.Net;

namespace Send_SMS
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void buttonSend_Click(object sender, EventArgs e)
        {
            string status = "";
            //CookieContainer cookie=

            CookieContainer cookie = Login.Connect(textBoxID.Text, textBoxPassword.Text, out status);
            string[] siteParameters = Login.GetSiteParameters(cookie);
            string messgeSentResult = SendSMS.Send_Processing(textBoxSendTo.Text, richTextBox1.Text, cookie, siteParameters);
            MessageBox.Show("Msg sent successfully..");
        }
    }
}