Facebook has begun rolling out an update to its Messenger app for iPhone that will allow users of the social network to start free voice calls with friends over a Wi-Fi or data connection. For now the new feature is only available to users in the US and Canada, with calls placed by tapping the "i" icon on the top right side of chat, and then hitting the "Free Call" button from your friend's contact card.

Your friends will need to have the latest version of Facebook's standalone Messenger app installed on their phone in order for the feature to work. The user on the other end will receive a push notification to accept or deny the call. Friends using the Messenger app should have a phone icon next to their names on your contact list, but there are no cues to indicate which ones you can actually call.

The new feature will be especially useful for people with spotty cell service at home or work and those hoping to save minutes. Sure, similar services are already available, some even offering video calling options. But once this becomes available in other countries and mobile platforms, Facebook could have one of the largest communities of VoIP users in the world, with all your contacts sitting conveniently in one place.

It's worth noting that Facebook has offered voice and video calling on its site since 2011 through a tie-up with Skype, but the tool wasn't made available on mobiles. The closest they got to offering voice communication on mobiles is a recent update to the Messenger app that allows users to send recorded messages.