use Symfony\Component\Notifier\Message\SmsMessage;
use Symfony\Component\Notifier\Bridge\FakeSms\FakeSmsEmailTransport;
use Symfony\Component\Mailer\Mailer;
use Symfony\Component\Mailer\Transport\NullTransport;

$texter = new FakeSmsEmailTransport(new Mailer(new NullTransport()), 'foo@bar.com', 'baz@foo.com'); // Normally from DSN

$sms = new SmsMessage(
  '+1411111111',
  'A new login was detected!',
  '+1422222222'
);

$sentMessage = $texter->send($sms);