>Download and Install the Facebook messenger app on your Android or iPhone from there store and Launch the messenger app on your device.

>You must have a recent conservation going with the person whom you are calling. Just tap on the Conservation to open it and if you don’t have any recent conservation tap on the compose message button placed at the bottom right and here you can add the person’s name whom you want to call.

>Type anything in the message and send it, to start the conservation.

>Now just tap once on Contact info button, placed at top right corner like image below . Now you will able to see the contact information whom you want to call

Here with Options like Timeline and others, you will see a Free Call button placed at the mid of the screen. As shown in the below image.

• Just Hit the Free Call button and you are done. You will be making free call to your desired contact.

That’s it, now you will be able to talk to your friends or relative for free of cost just using an internet connection. International calling rates are very high for US, UK and Canada, so for calling in those countries you can use this Facebook calling feature for absolutely no cost. But you have to keep the Push Notification On so it should alert your when someone is calling you.