WhatsApp Calling Feature Invites

Turns out that WhatsApp is slowly rolling out voice calling features in the latest version of whatsapp to global users. The version you will have to install is 2.11.508, available for download from the official website (and not Google Play store). The problem is that the feature isn't enabled by default and you need to have someone 'invite' you to be able to use the feature. Of course, it won't be useful because the person you want to make a call to needs to have the feature enabled too!

There is no concrete information on how to enable the calling feature in the latest build and how the invite system works. It's likely that whatsapp is enabling the voice calling feature randomly - so people will have to wait.

If someone here has figured out how to enable voice calling, please post the tip/trick and share/request invites.