WhatsApp Messenger allows you to send free text messages over the internet, saving you the cost of sending SMS. You can use WhatsApp Messenger to send messages over WiFi or 3G to anyone else with the app installed on their phone. The software works across mobile operating systems (iPhone, Android, BlackBerry, etc.) so it will function with contacts who have other versions of WhatsApp Messenger installed.
Compatible with Blackberry OS.
Download from here.