Facebook's Messenger app for iPhone has undergone a number of facelifts in the past year or so, but a new feature was added today that may completely change the way you use it: free calling over a data connection. The Verge reports that the new feature began rolling out to users today, and doesn't require you to update the app itself.
The new calling option is a rather streamlined affair: Simply open up a conversation with one of your Facebook friends from the app's menu, select the "i" icon in the corner and then hit the "Free Call" button. The recipient will get an alert window letting them know that you are calling.
The calls won't count against your phone's minutes, but it will eat up some mobile data if you're not connected to WiFi, so while the call may be free as far as Facebook is concerned, it's important to keep an eye on your data usage. The new feature is currently only available to US-based Facebook users, and no word on an international release is available at this time.