Also, you can't access 911 and other emergency service numbers through WhatsApp).
Switch from SMS to WhatsApp to send and receive messages, calls, photos, videos, documents, and Voice Messages. WhatsApp uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message and call friends and family. WhatsApp Messenger is a FREE messaging app available for Android and other smartphones.