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. Contact your wireless carrier for details about international roaming countries, SIMs, rates, and policies. If you do not have an international data plan, turn off cellular data when roaming to avoid data roaming charges.
We recommend you configure WhatsApp so that it only connects to Wi-Fi networks when your phone is roaming. However, with this configuration, you will not receive messages while you are roaming and without Wi-Fi.
To avoid extra data charges when roaming, you can disable Media auto-download for images, video, and audio. To learn how to configure Media auto-download read this article.
WhatsApp Support Team