Another tool/service that will come in handy for Facebook at Work as well -- free group calls for up to 50 participants
"Jump on the party line or hear the voices of your whole family with Facebook Messenger’s latest feature. Rolling out globally over the next 24 hours on Android and iOS for free, users can start a group VoIP audio call from any group chat.Facebook Messenger launches Group Calling to become your phone | TechCrunch
Just tap the Phone icon, select which of the group chat members you want included and they’ll all receive a Messenger call simultaneously. If you miss the initial call but it’s still in progress, you can tap the Phone icon in the group chat to join the call. At any time you can see who’s on the call and send another ping to anyone who hasn’t joined."