So after a long time finally whatsapp calling APK has been released. You just need to install it and it will automatically have the calling feature! Its just that simple. Here is a screenshot showing the same.
How to Use this APK to make Voice Calls ?
Download the WhatsApp APK from the link given at the bottom of this article.
Uninstall the previous version of WhatsApp if you have installed any.
Now Go to Settings > Security > Allow Unknown Sources. Now you can install APKs from different sources.
Place the downloaded APK on your Android device.
Tap on the downloaded APK and complete the installation process.
Once completed, start the app and now you have WhatsApp with Voice Calling feature
Download link : http://www.dropbox.com/s/a2ldp1xya1un32j/Whatsapp-2.12.14-%20With%20Improved%20Performance%20and%20Voice%20Features%20Enabled.apk?dl=0