Facebook’s Mark Zuckerberg has repeatedly shot down rumors the company is building its own phone, but the latest update of Facebook’s main iOS app released Friday turns the social network into a telephone system by enabling free Internet calls within the United States and Canada. Facebook for iPhone now doubles as a way to phone a friend for free.

The company introduced voice calling in January to its standalone Messenger app, The social network recently released version 5.5 of its iPhone and iPad application to allow for free friend-to-friend voice calling in the U.S. and Canada.

Sure, that means using a phone as a phone. But if you’re using WiFi, you’re bypassing your mobile carrier and getting audio that sounds much clearer than a regular call. But watch if you’re not on WiFi, because then you’re going through your existing data plan.

The voice-over-IP functionality extends a feature that was first introduced on Facebook Messenger to even more of the social network's mobile audience. The feature, which should appeal to teens and cheapskates, could help the social network keep the attention of its youngest users, some of whom have, according to a recent SEC filing by the company, "reduced their engagement with Facebook in favor of increased engagement with other products and services such as Instagram."

Just as with Messenger, people can navigate to a pal's contact info -- click the friends tab, pick a buddy, and hit the "i" button on the top right corner and look for the button enticingly marked "Free Call". If the friend is online and also has the upgraded app, you can connect and make the free voice call.

In version 5.5, Facebook also tweaked its like, comment, and share buttons to encourage people to engage more with status updates.