WhatsApp - Free phone messaging

[quote="casasespania"]lol.
Not used Viber for a year or so- it was a PTT system (push to talk) when I used it last- not sure if its fully 2 way/ bi-directional conversational now?
(You basically recorded a message and it sent that and waited for a reply from the other party)[/quote

It's a normal phone conversation now. We use it often, especially abroad, as it's free calls when on WiFi.