Windows Phone. Account and Profile.
Is it free to send messages over WhatsApp?
WhatsApp
 uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as 
available) to send and receive messages to your friends and family. You 
don't have to pay for every message. As long as you haven't exceeded 
your data limit or you're connected to a free Wi-Fi network, your 
carrier shouldn't charge you extra for messaging over WhatsApp.
WhatsApp Calling works in the same way.
Please be aware that:
WhatsApp Calling works in the same way.
Please be aware that:
- If your phone is roaming, additional mobile data charges may apply.
- If you send SMS messages to your friends inviting them to use WhatsApp, service charges from your mobile provider may also apply.
