Now you can go into any group chat, and look to the top right corner. A call button has been added there, much like in individual chats. Tap on that in a group chat, then selecting the people you want in a call, and you’ll have a group call going already. There’s also the option to make a video call from there.
That said, the feature is still limited to only four people in a group call. And the quality of the call will depend on the person with the weakest connection. On the flip side, calls are also end-to-end encrypted, so if you’re worried about privacy there’s that still going for it. The feature is now available on iOS, while the Android is still in the works and will be coming “soon”. (Source: TechCrunch)