1. Facebook Messenger
Viber is also a very similar to WhatsApp as it uses mobile contact numbers to identify users. You get an access code sent to your mobile number via SMS. It’ll then check your contacts to see if any of your contacts are connected to Viber; you can then instantly connect with them. Unlike WhatsApp, Viber allows you to call users, provided your smartphone is connected to the Internet. This app works with iOS, Android, Windows Phone, BlackBerry Nokia and Bada.