Currently free for iOS users; one year free for Android users and then $1 per year
WhatsApp Messenger is a cross-platform mobile messenger that allows you to exchange messages without SMS fees.
Short Message Service (SMS) is a text messaging service component of phone, web or mobile communication systems. If you send a text message on your cell phone, chances are it’s via SMS. Depending on your cellular service plan, you pay per SMS message, for a certain number of messages each month or even for unlimited SMS messaging. However, these plans normally don’t extend to texting international subscribers. Some companies have gotten around this by developing their own messaging services that don’t use SMS, thereby avoiding the costs associated with texting even internationally. Apple’s iMessage service is an example of this type of service; however, these services’ chief shortcoming is that you must be communicating with someone else on the same operating system. Therefore, an iOS user avoids using their SMS allotment only if they iMessage with another iOS user.
WhatsApp Messenger is a free cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. It’s available for iPhone, BlackBerry, Android, Windows Phone and Nokia, so you can communicate across different platforms without incurring SMS charges. It uses the same internet data plan that you use for email and web browsing, so there is no extra cost to send a message.