Though I do have a phone, I do not use WhatsApp. I get the same responses you are getting - people absolutely can not believe that we function in society.

I do not use WhatsApp, Instagram, or FB.

You pay a price (we miss many party invitations, only one friend consistently emails us and FB everyone else), but it's worth it.

Recently spoke to a colleague in Italy that told me he hates WhatsApp, but is forced to use it because the school of his kids in Rome use it as sole means to communicate, despite this being a legal violation (public organizations in Europe must use GDRR-compliant tools).