What's also in violation of GDPR is sending your contacts to Whatsapp, as the app nags right and left to do, and as Whatsapp claims would be required for unrel

What's also in violation of GDPR is sending your contacts to Whatsapp, as the app nags right and left to do, and as Whatsapp claims would be required for unrelated functionality such as seeing those freaking Whatsapp/Fb status pages of others or publish your own I guess. Phone numbers are PII, so even if you have individual consent for every number or number/name pair to pass onto third parties, which I very much doubt you have, the holder of that data in addition has a right to request data stored at Whatsapp/Fb and cancel storage and processing.