Although Facebook previously had Wi-Fi calling enabled on their Facebook Messenger app, the option to use it was limited to the US, UK and Canada. To expand on that capability, Facebook has now updated Messenger to v4.1 and is offering free calls over Wi-Fi wherever you are.
What's New in Version 4.1
Free Calls: Talk as long as you want and stay in touch wherever you are. (Calls are free over Wi-Fi. Otherwise, standard data charges apply).
It's a small change to the app but one I'm sure a lot of folks looking for cheap calling or a Skype alternative will appreciate. The update is live in the iOS App Store right now and you can grab it via the link below. Let us know how it works for you after you get it downloaded.