And then there are people who just use a Google Voice number on Whatsapp instead of a real phone number, and many don't even have a phone number listed on Facebook. I'm actually surprised that anybody would give their real phone number to Facebook, Whatsapp, or any of the other "social networks"...
But you can give Whatsapp a Google Voice number instead of your real phone number. That way if they decide to sell it as part of your profile, you can easily change/cycle it (or apply better filtering, DND, etc.)
