Step 1: Download latest version of WhatsApp for Android
(2.11.561) from the Play Store
Step 2: Ask a user who has the feature to
call you..
Step 3: After receiving your call, close the
app and reopen it.
Step 4: Check out the new tab for calls.
From here, you can call your buddies over VoIP, and the more people you call,
the more it will spread.
You can then
call any of your WhatsApp contacts over VoIP through the app. You may not be
able to reach people running older versions of the app