It appears that the most awaited feature on Whatsapp is finally rolling out to users worldwide. A user on Reddit has shared some screenshots of Whatsapp calling feature. We are though not yet sure if this feature is rolling out to all users or it is though some kind of invite system. We were unable to reproduce that feature on our Nexus 4 by using the latest apk file from the Whatsapp website.
Checkout the screenshots below to check how the calling feature looks like.
As you can see from the screenshots above, the feature appears great, but the UI appears like Google Hangouts. We are still not sure how the calling feature works, but will update you as and when we get it working on our devices or hear more from whatsapp.
We will update the post when we have more info.