The AndroidPit test has revealed that WhatsApp voice callings, which have been available on Android since the start of the year but were only recently added to the iPhone app, uses 1.3Mb of data per minute.

Chatting away at a rate of 1.3Mb of data per minute will burn through a 500MB monthly data plan in just 6 hours, which is equal to 11 minute of call-time per day.

However, by contrast, instant messaging and Voice over IP app Viber claims to use 240Kb per minute during phone calls.

WhatsApp is ruling the social app world with 800 million active users every month. The figure makes WhatsApp one of the world's largest social networks, bigger than Twitter's 284 million or even the photo-sharing service Instagram, which counted 300 million users.

Facebook itself, however, is still bigger, and tallies 1.3 billion users signing in every month. WhatsApp had also support team indicated that the feature for voice calling for them is in developmental stage.