Let good users in. Keep bad actors out with Verify API.

# Download the helper library from https://www.twilio.com/docs/python/install
import os
from twilio.rest import Client


# Find your Account SID and Auth Token at twilio.com/console
# and set the environment variables. See http://twil.io/secure
account_sid = os.environ['TWILIO_ACCOUNT_SID']
auth_token = os.environ['TWILIO_AUTH_TOKEN']
client = Client(account_sid, auth_token)

verification = client.verify \
                     .v2 \
                     .services('VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX') \
                     .verifications \
                     .create(to='+15017122661', channel='sms')

print(verification.sid)

<?php

// Update the path below to your autoload.php,
// see https://getcomposer.org/doc/01-basic-usage.md
require_once '/path/to/vendor/autoload.php';

use Twilio\Rest\Client;

// Find your Account SID and Auth Token at twilio.com/console
// and set the environment variables. See http://twil.io/secure
$sid = getenv("TWILIO_ACCOUNT_SID");
$token = getenv("TWILIO_AUTH_TOKEN");
$twilio = new Client($sid, $token);

$verification = $twilio->verify->v2->services("VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX")
                                   ->verifications
                                   ->create("+15017122661", "sms");

print($verification->sid);

// Download the helper library from https://www.twilio.com/docs/node/install
// Find your Account SID and Auth Token at twilio.com/console
// and set the environment variables. See http://twil.io/secure
const accountSid = process.env.TWILIO_ACCOUNT_SID;
const authToken = process.env.TWILIO_AUTH_TOKEN;
const client = require('twilio')(accountSid, authToken);

client.verify.v2.services('VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
                .verifications
                .create({to: '+15017122661', channel: 'sms'})
                .then(verification => console.log(verification.sid));

// Install the Java helper library from twilio.com/docs/java/install

import com.twilio.Twilio;
import com.twilio.rest.verify.v2.service.Verification;

public class Example {
    // Find your Account SID and Auth Token at twilio.com/console
    // and set the environment variables. See http://twil.io/secure
    public static final String ACCOUNT_SID = System.getenv("TWILIO_ACCOUNT_SID");
    public static final String AUTH_TOKEN = System.getenv("TWILIO_AUTH_TOKEN");

    public static void main(String[] args) {
        Twilio.init(ACCOUNT_SID, AUTH_TOKEN);
        Verification verification = Verification.creator(
                "VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
                "+15017122661",
                "sms")
            .create();

        System.out.println(verification.getSid());
    }

curl -X POST "https://verify.twilio.com/v2/Services/VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Verifications" \
--data-urlencode "To=+15017122661" \
--data-urlencode "Channel=sms" \
-u $TWILIO_ACCOUNT_SID:$TWILIO_AUTH_TOKEN

// Install the C# / .NET helper library from twilio.com/docs/csharp/install

using System;
using Twilio;
using Twilio.Rest.Verify.V2.Service;


class Program
{
    static void Main(string[] args)
    {
        // Find your Account SID and Auth Token at twilio.com/console
        // and set the environment variables. See http://twil.io/secure
        string accountSid = Environment.GetEnvironmentVariable("TWILIO_ACCOUNT_SID");
        string authToken = Environment.GetEnvironmentVariable("TWILIO_AUTH_TOKEN");

        TwilioClient.Init(accountSid, authToken);

        var verification = VerificationResource.Create(
            to: "+15017122661",
            channel: "sms",
            pathServiceSid: "VAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
        );

        Console.WriteLine(verification.Sid);
    }
}