title: Twilio - Give warning message to ongoing conference call
body: <p>I am basically using twilio for creating conference call, usually the call is of about 30 minutes. Is it possible to play a warning message to conference call which say : <strong>Warning, Your 30 minute call is about to end after 5 minutes</strong>. I want to give the warning message after 25 minutes of call start and I also want to give warning message to all the participate in conferences.
  I would be grateful if someone refers me to that part of documentation.</p>