One of the great things about WhatsApp, is its relative low cost for sending messages from one user to another. But the application can also be used to make phone calls, something that we initially thought not many WhatsApp users actually utilise. As it turns out, phone calls via WhatsApp is quite popular, with the company recently announcing that it's passed the 100 million phone calls per day milestone. 

With an estimated 1100 calls per second, it's quite the feat for an application which has until recently only been seen as an IM (Instant Messaging) tool. Even more impressive is the fact that the phone call service for iOS and Android devices has only been available on WhatsApp for a little over a year, which means that its daily active phone call users is growing faster than Skype, according to The Next Web.

WhatsApp currently has more than 1 billion users signed up for its service, which has prompted the company to stated that more features around phone calls are imminent.