If you've been sitting, wishing and waiting for your Android handset to let you make free data-based calls, then today's your lucky day. Our chums over at Engadget Spanish have discovered that WhatsApp's long-promised voice calling is now available on Android. Once updated, Facebook's app provides a new tab that'll let you dial friends on top of texting them. So how does it work? I gave it a whirl over here in France, calling my colleague Richard Lai in Hong Kong. Though the quality was clear, there were a couple of technical glitches. On one call, a one-to-two second delay made a conversation challenging, and on another, Richard complained about an annoying echo. Several other attempts were problem-free.