WhatsApp calling feature has been launched for Windows Phone now. The latest update has been released on June 23 that enables internet calling option for Windows Phone users on WhatsApp. Earlier Windows Phone users was not able to share voice messages as well, but this update also enables voice/audio sharing feature on Windows Phone. You can download the latest version (22.214.171.124) from Windows app store that weighs around 17 MB.
You will need to have Windows 8 or later version to enjoy WhatsApp calling feature. WhatsApp calling is based on VOIP that usage internet connection. It is completely free by WhatsApp, but you may get charged for data by your carrier.
Android was the first platform to receive WhatsApp calling feature, then iOS users got the update, and finally Windows Phone users can enjoy this feature, and make calls to theirs friends and family around the world.