Activate voice calling feature in Whatsapp - Steps
1. Download the <a href="https://play.google.com/store/apps/details?id=jackpal.androidterm&hl=en" target="_blank" rel="noopener noreferrer">Terminal Emulator for Android - Apps on Google Play</a> for Android.
2. Ensure that you have the latest version of Whatsapp: #-Link-Snipped-#
3. Load terminal emulator and type the following command in the console:-
su am start -n com.whatsapp/com.whatsapp.HomeActivityThis unlocks the voice calling feature in whatsapp. But the magic doesn't start unless someone who's already enabled the feature on their phone gives you a call. No you and your friend can't mutually enable this feature on your phones by enabling and then calling. Think of it as an 'invite' model wherein someone who's received a call on whatsapp and enabled the voice calling feature needs to call you to get this feature activated. Trust me, this is the worst part of the entire process. It's like having a cake in your hand but you can't eat it!
I will not encourage anyone to share their phone numbers publicly - because it will only attract spammy messages to your phone. I'd strongly recommend that you should wait until this feature is made available by default to every user - and I guarantee that it won't be too long before it's done.
PS: If you perform above steps, you will see calling feature but it won't list any entries in the 'contacts' section. This is because the feature is invite only and you need to have someone who's enabled this feature on their phone to call you. I hope you got the point.