Whether you want to make a video or audio call on WhatsApp, Android users can ask Google Assistant to make the call for them. Google's virtual assistant interfaces with different third-party messaging services, so this addition doesn't come as a surprise. The caveat is that it only works through Android, for now. We presume the feature could make its way to other Google Assistant-supported devices, but for now, you need to have an Android smartphone. All you need to say to have Assistant make the call is "Hey Google, WhatsApp video [insert name of contact]."
Source: 9to5Google