acebook already has your eyeballs. Now it wants your ears too. Starting this week, whenever users in the U.S. boot up Facebook's Messenger app on iOS, they'll be able to make in-app phone calls to anyone else with an iPhone. For free. 

The Verge reported the news late Wednesday after noticing that a Free Call button had suddenly appeared in the application (to get to it, hit the "i" icon in the corner). The social network had previously tested free voice calls in Canada, and promised that a stateside version was on its way. Android owners are out of luck for now, but expect the feature to become available soon. 

Of course, free phone call apps are nothing new. Google Voice, Gmail, and Skype have been offering free in-app calling for some time. But Facebook is different: The slice of smartphone owners who are also on the billion-person-plus social network is considerable and growing larger by the day. Although Skype and Google offer perfectly fine apps in their own right, no one's been anointed "The Next Big Thing in Free Phone Calls" yet. It's still anyone's game. 

Moving into voice calls is a smart move for Facebook, even if recent studies have indicated that people are decreasingly using their phones for conversation. (Time spent talking on your phone falls decidedly behind browsing the internet, checking social networks, playing games, and listening to music — in that order.) Facebook, which just this week unveiled an impressive new Search feature, has been trying to get phone owners to use dedicated apps like Facebook Messenger and Facebook Camera for some time now, to varying degrees of success. And Robert Hof at Forbes points out that the feature could finally squelch rumors that Facebook is working on its own phone, even though CEO Mark Zuckerberg has denied the existence of a "Facebook Phone" time and time again. "Nobody really needs an actual Facebook phone," says Hof, "because apps make every phone a Facebook phone."  

For consumers that's great news. It means there's little reason to pay for minutes ever again. Facebook's Messenger app is currently available for free in the Apple App Store.