title: What are Facebook Messenger audio message formats?
body: <p>I'm using Facebook Messenger to send an audio file to my bot. The webhook call that Facebook sends me includes a URL, which is the audio file and when I download it it's in .mp4 format (weird, since it's supposed to be audio not video).</p>
  
  <p>I didn't find any documentation as to why it's .mp4, and whether there is the option to get a different format from Facebook. Anyone knows anything about this?</p>