I can't believe that anybody would recommend WhatsApp for any kind of secure messaging. The app is closed source, and there's absolutely no way to audit that it implements the protocol faithfully. Facebook can easily be spoofing keys, there's already a story regarding this type of vulnerability https://www.theguardian.com/technology/2017/jan/13/whatsapp-...

Say what you will about Telegram, but at least you're getting what's advertised. WhatsApp is a complete black box that's owned by a predatory company whose business is selling user data.