Free your calls! Call anyone, anywhere. International free calls to other Viber users using 3G or Wi-Fi. Check your contacts, you can see which of your iPhone contacts is already on Viber. Go ahead and call. It's free* and it works great! * Calls use your data plan Viber is an iPhone app(Android and Blackberry versions coming soon!) that lets you make free phone calls to other iPhone users that have Viber installed. When you use Viber, your phone calls to any other Viber user are free, and the sound quality is much better than a regular call. You can call any Viber user,anywhere in the world, for free. All Viber features are 100% FREE and do not require any additional "in application" purchase. source: http://www.viber.com/