Facebook has been working on some new things, including a fresh search which currently is in beta, but is surely needed. On the mobile front, it has added free Voice Calls for all US iPhone Facebook Messenger users. No update is needed from the App Store and it seems to be simply enabled as of today, as long as you have the recent app and reside in the US. So in short, you will be able to call other Facebook users for free over WiFi or your data connection. The Verge reports that the call quality sounds "very good" and is "certainly on par with competitors Viber, Vonage and Skype".