text: In the Windows Phone 8.0 and earlier version , the developers could utilize the SMSComposeTask to send SMS from the Windows Phone App. If you are targeting the Windows Phone 8.1 Silverlight model , this will still work fine . How about sending SMS from Windows Runtime App ?
  How to Send SMS in Windows Phone 8.1 XAML(Windows Runtime) App ?
  If you are targeting the Windows Phone 8.1 XAML App(Windows Runtime App) , you can use the ChatMessage class defined in the Windows.ApplicationModel.Chat namespace.
  Below is a sample code snippet demonstrating how to send SMS from a Windows Phone 8.1 App.
  async private void Button_Click(object sender, RoutedEventArgs e) { ChatMessage chat = new ChatMessage(); chat.Body = "Subject : This is a Test SMS from developerpublish.com"; chat.Recipients.Add("000000"); await Windows.ApplicationModel.Chat.ChatMessageManager.ShowComposeSmsMessageAsync(chat); }