The popular mobile messaging service WhatsApp has finally updated its iPhone iOS app with a free voice calling feature.

Already available on Android devices, the “WhatsApp Calling” feature is comparable to Skype and the FaceTime Audio service on iOS mobile platform.

The calls are free, running on your data connection or Wi-Fi, Forbes reported. The new feature will be available for every iOS user within the next few weeks.

“Call your friends and family using WhatsApp for free, even if they are in another country. WhatsApp calls uses your phone’s Internet connection rather than your cellular plan’s voice minutes,” the WhatsApp team posted in the app update description.

This is how it works. If someone calls you through WhatsApp, you will see a push notification from the messaging service showing, who the call is from.

Once you answer the call, you will notice that there are options to mute the call or put it on the speakerphone.

You can also send a message to the person calling you.

WhatsApp, owned by Facebook, has 800 million monthly active users.

It makes WhatsApp one of the world’s largest in terms of active users, bigger than Twitter’s 288 million active users.

Facebook now has about 1.4 billion monthly users and Facebook Messenger has roughly 600 million users.