GROUP VOICE CALLS will be one of the next features!
Unfortunately there is actually nothing that we can show you as abovementioned, seen that WhatsApp is internally working on it, but when WhatsApp will add something more that will be possible to show, we will immediately publish all screenshots and information.
We can already tell that, seen that this feature requires a lot of development, it will be available for the next year, so don’t expect too much to see this feature in WhatsApp soon. WhatsApp has other priorities right now, for example the imminent RECALL release.

more details here � http://www.dominzyloaded.com/2017/10/whatsapp-plans-to-introduce-group-voice.html