Inspired from here: https://www.twilio.com/docs/api/rest/incoming-phone-numbers?code-sample=code-get-an-incomingphonenumber&code-language=php&code-sdk-version=5.x
Example code to delete()
a Twilio phone number:
<?php
// Get the PHP helper library from twilio.com/docs/php/install
require_once '/path/to/vendor/autoload.php'; // Loads the library
use Twilio\Rest\Client;
// Your Account Sid and Auth Token from twilio.com/user/account
$sid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
$token = "your_auth_token";
$client = new Client($sid, $token);
// Delete a Twilio number based on its sid. If you do not have a sid,
// check out the list resource examples on this page
$number = $client
->incomingPhoneNumbers("PN2a0747eba6abf96b7e3c3ff0b4530f6e")
->delete();
Warning: Once the number is deleted, any code using it, won't work. Be sure you really want to run the code above.