Facebook Messenger app on an iPhone with new "Free Call" button. Image: Joanna Stern/ABC News

No, Facebook didn't announce a phone or its big mobile plans on Tuesday, but it does have a little something phone-related to share today. As first reported by The Verge, Facebook is rolling out a free calling feature in its Messenger app for the iPhone. The feature, which was released in Canada a few weeks ago, lets iPhone users make free calls to other iPhone users who are using the Messenger app. You can't call landline or cellphone numbers.

The update will begin rolling out today in the Messenger app. In the app, select a friend, then the "i" icon in the upper right hand corner, and you will then see a "Free Call" option. Facebook confirmed to ABC News that users will not have to update the app for this feature; it will automatically appear for those who already have the app. As with Skype or other mobile VoIP (Voice over Internet Protocol) services, you can make the calls over Wi-Fi or a 3G, 4G or LTE connection. Wi-Fi is the cheaper option; if you are on a cellular network it will eat at your data plan.

MORE: A Facebook Phone? Social Network Testing Voice Features

This is just one of many mobile announcements Facebook has made in the past few months. It upgraded both its iPhone and Android apps to make them faster and it released is new Poke app, which destroys messages 10 seconds or less after you look at them.

Of course, Facebook has long been rumored to be building a phone of its own, but as we said a few weeks ago, it looks like the social network is already transforming our phones into Facebook phones - or building its own right in front of our faces.

On Tuesday at a big event at its headquarters, Facebook announced its new Graph Search feature, which turns the personal information people have shared on the social network into a powerful searchable database. While it is only rolling out on a limited basis in the U.S. right now, ultimately it will allow everyone to search easily across the network and their friends' information.

Facebook didn't make a big announcement about the voice calling service, but it's a very big move for the social networking company. While Facebook declined to comment on whether Messenger app calling would come to Android or the Web, or if it might charge for the service, it is a step into voice calling for the company and a further step into mobile products.