title: Twilio not delivering sms messages to some users
body: <p>I set up a scheduling website at work which uses <a href="https://www.twilio.com/" rel="noreferrer">Twilio</a> to send out sms messages with each person's next day assignment information as well as a link to the website where notes and everyone's next-day assignment is posted.  Occasionally colleagues complain that they haven't received messages.  Recently the problem has gotten much worse though is to be limited to people with AT&amp;T and Sprint.  People with Verizon and TMobile are get their messages without a problem.  </p>
  
  <p>A few more facts:</p>
  
  <ul>
  <li>All of my code works well in testing and is consistent with Twilio's
  instructions. </li>
  <li>Twilio's logs list the messages as having been sent.</li>
  <li>The people who's sms messages are not delivered tend to be at the end
  of the alphabet</li>
  </ul>
  
  <p>Anyone have any ideas what might be going on?</p>