Well done, @redstarfish!
It helps every time we say "no".
I really don't like how common WhatsApp had become, and refusing to use it has become a social challenge.
By the way, when someone invites you to WhatsApp, do you offer an alternative? Do you invite them to use something better, or do you at least explain shortly why WhatsApp is not acceptable? (I usually don't, I often just say no and move on, but I'd like to do more).