WhatsApp has rolled out its new free voice-calling feature to a few users India which appears to be available on invite-only basis, as of now. The invite-only basis basically means that users will get a call through WhatsApp from someone who already has the feature updated. The feature is also restricted to Android only and you will need the updated 2.11.508 version to access the app. According to the images posted, users who receive the voice-calling feature will notice an icon for it, beside the Chats and Contacts tabs. The call interface seems to quite similar to a smartphone’s contact directory. The app keeps a record of recent WhatsApp calls as well. Facebook, which bought WhatsApp last year, recently revealed that the app has 700 million monthly active users and that over 30 billion messages are shared on WhatsApp everyday. With voice-calling feature coming soon, it’s likely that WhatsApp’s engagement number will rise further.