When I travel abroad / overseas, will I be charged for data roaming?
WhatsApp Messenger uses the same internet data plan as web browsing and email on your phone. If using your cellular data while roaming will normally result in additional charges, you may be charged extra by your mobile provider for using WhatsApp while roaming.
However, provided you have Wi-Fi internet access and current WhatsApp service, WhatsApp should be free to use over a Wi-Fi connection. To confirm that your data roaming is disabled:
Android 2.1 and 2.3:
Settings > Wireless & networks > Mobile networks and make sure Data Roaming is disabled.
Settings > Data usage > Menu Button > and make sure Data roaming is disabled.
Non stock Android:
Look for "Network" or "Data" in your phone settings and disable the "Data roaming" option.
We recommend that you set your WhatsApp status to "I am currently roaming abroad, will reply when I am on Wi-Fi" -- this way your friends will know why you are not answering right away.
WhatsApp Support Team