This project demonstrates how simple it is to burn a phone number and also describes how to mitigate such attacks. I am not responsible for any criminal use of this code. It is solely meant for educational purposes. This script when run will send text messages to the specified targets every 2 seconds. Normally several thousand text message requests could be sent per second, but because this utilizes wireless provider API's doing so would cause your server to be blacklisted.
<?php
require_once "Burner.php";
$targets = ["8005551234", "8005556789", ];
$messages = ["Hello World A", "Hello World B", "Hello World C", ];
$dos = new Burner($targets, $messages);
$dos -> attack(5000);
?>
Apple iPhones at least allow you to filter out phone numbers not in contacts. Sadly, not enough people know of this simple fix.