How can I block iPhone calls but allow WhatsApp messages?

i want to be able to block standard calls from a contact in my iPhone contacts but allow them to what’s app me. There appears to be a link between the two.

if I go into the iPhone contacts and block someone it’s blocking their phone call and texts as expected - But it is also blocking their what’s app calls but allowing what’s app texts. Any idea why it’s blocking what’s app calls and how to stop it.

I have seen others stating the same problem.

[Re-Titled by Moderator]

Original Title: Blocked contact blocks wots app