Send SMS to fixed mobile number using C# in ASP.Net

How to send sms on fixed mobile number using asp c#

I have textboxes. While user fill all text boxes details and click on submit button then sms sent to fix mobile number.

namespace SmsSend
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
 
        }
        protected void btnSend_Click(object sender, EventArgs e)
        {
            string countrycode = DropDownList.SelectedValue.ToString();
            string number = TextBox1.Text;
            string destinationaddr = countrycode + number;
            string message = TextBox2.Text;
            string result;
            String massage1 = HttpUtility.UrlEncode(message);
 
            using (var wb = new System.Net.WebClient())
            {
                byte[] response = wb.UploadValues("myapi", new System.Collections.Specialized.NameValueCollection()
                {
                    {"apikey","29593928211702653340"},
                    {"number","destinationaddr"},
                    {"message","massage1"},
                    {"Sender","MUNPLA"},
 
                });
 
                result = System.Text.Encoding.UTF8.GetString(response);
            }
 
            Label3.Text = "SMS Sent to " + destinationaddr + " Successfully"; 
        }
    }
}