Here’s what you need to do:
Step 1: Grab the latest version of WhatsApp for Android (2.11.561) from Here 
file id: 43138
Step 2: Ask a user who has the feature call you through WhatsApp. You might have to ask friends of friends or associates, but as it spreads, more and more people will be able to get in on the act.
Step 3: After receiving your call, shut WhatsApp down and then re-open 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.