Yes they have been automatically enabled by WhatsApp (I suppose) to have it enabled. With them, they can now call anyone with Android or Blackberry apparently also, to activate their WhatsApp call function.
This is a data call (Also known as IP call). This is not same as the default when you press the phone icon and call it uses the celluar call.
Here's two way you can do it.
- Update your WhatsApp to at least version 2.11.561.
- Ask someone with a call function enable to give you a WhatsApp call.
- Pick up the call from WhatsApp.
Beware there are spam calls going around as well. So be careful not to pick up those.
2) source: http://www.androidpit.com/whatsapp-call-feature-here-s-how-to-get-whatsapp-voice-calling
- Enable Settings>Settings>Unknown Sources. (Remember to disable after)
- Go to WhatsApp website and download the latest Android file version 2.12.19.
- Install the downloaded file.
- That's it.
Apple users will have to wait as when you try call any Apple user, you will see the notice similar below.