At a bare minimum, dont open them, just delete them block the sender domain and username, and I would at least temporarily cancel and delete anything you have to do with whatsapp (there are plenty of other messaging services to use) to break the chain. You can contact any whatsapp contacts you want to keep informed via normal text, email, or whatever telling them why, and if you still need whatsapp reinstall it in the not too distant future.
It sounds like they are just phishing and hoping you bite, so imo you'll be okay with these few steps.
Caveat I'm not an expert by a million miles.
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