Skype (15 MB), make free Skype-to-Skype calls over 3G or WiFi network on the move, or cheap calls to landlines or mobile phones at Skype rates. No video calls is available and some handsets may not be supported.LINE (11 MB), a light and popular messenger supports both free messaging and voice calls. Features include automatically identify your friends using LINE, send photos, unique stickers and emoticons, create or join group chat rooms.Tango Text, Voice, Video Calls (13 MB), make free voice and video calls over 3G, 4G and WiFi network on the move. From my contacts, it automatically finds the friends I can Tango. More mobile devices are supported but the desktop client has yet to be developed.