What is the group call feature?
Group call is a mVoIP-based feature that enables you to talk with your friends in a group of 3 to 5 people in a chatroom. 
If your device does not have a built-in microphone (e.g. iPod Touch), please connect a microphone. 
(We recommend that you make calls on a Wi-Fi network to ensure the best call quality and to avoid carrier network data charges. 
Please contact your service provider for more information as data charges may vary depending on the carrier.)