Facebook 5.5 for iOS has just been released, and with it comes free voice calling for North American users over Wi-Fi and cellular networks. The feature came to Facebook's separate messaging app a couple of weeks ago, and is now baked in to the full-fledged Facebook iOS experience for users across the US and Canada. After updating, simply open your chat pane by tapping the icon on the upper-right, select a friend, and then select "Free Call." As you'd expect, the person on the other end also needs to be located in North America, and also needs to have the latest Facebook app installed. It's a nice way to make voice calls without tapping into your voice minutes--just make sure to keep an eye on your data plan when you're away from Wi-Fi, no need to try to save on voice minutes, only to rack up massive data usage fees, you feel me?