According to Mashable, you are now able to call your friends using the Facebook App!
Free calls are placed by tapping the “i” icon on the top right side of chat, and then selecting “Free Call” from your friend’s contact card. Your friends will need to have Facebook’s stand-alone Messenger app installed on their phone in order for the feature to work (otherwise the “Free Call” icon will appear grey and marked out).
Tell us, is this a feature that you would use?