Now WhatsApp users can call each other - provided they have an Internet connection - for free.
Users simply click on the "Calls" tab to phone a friend, who can be located anywhere around the world. But this works only when both parties are on the latest version of the app and have an Internet connection: Wi-Fi or mobile data.
With the new feature, WhatsApp joins the ranks of competing apps like Viber, Skype and Apple FaceTime - services which have been eating into telcos' traditional business revenue, including voice calls and SMS.