The calling feature in the chat group is already available on Facebook Messenger, another messaging app that is under Facebook, which has WhatsApp.
Calling features in the chat group on WhatsApp can prove very useful for chatting with more than one person simultaneously. However, this feature can also be annoying if misused. For example, when you are busy and people in your group are busy calling.
Facebook is also actually developing a video chat application called Bonfire. Unfortunately, only a small percentage of people can use the app right now. The voice call feature in the chat group should come out earlier than the video call feature in the chat group.
Meanwhile, WhatsApp will also launch a feature of pulling back messages to its users. Prior to this it has been reported that a feature called "Delete for Everyone" has been tested and may be available in the near future.
Once the feature is launched, users will be able to recall the content they have submitted, whether text, images, video, GIF documents, or even status.