title: Incoming Voice Webhook is getting called twice for the same call
body: <p>Trying to understand why the incoming voice call webhook is getting called twice. </p>
  
  <p>The phone numbers's voice webhook url is set up to point to my backend and the api endpoint rejects the call right away as follows. </p>
  
  <pre><code>const voiceResponse = new VoiceResponse();
  voiceResponse.reject({ reason: 'busy' });
  res.type('text/xml');
  res.end(voiceResponse.toString());
  </code></pre>
  
  <p>However, the same call with a different CallSid is pinging the webhook again after a couple of seconds. </p>