When someone becomes annoying or you no longer want to have communication with that person, the first thing that usually comes to mind is to block them. Blocking has been a feature for ages and it doesn't let you have anything to do with a contact.
What happens when you block someone on WhatsApp? | TechInsider
When you block someone on your Android or iPhone, either through the phone app, their caller ID is hidden in your call history and stops calls from connecting.
It's impossible to literally block numbers on the carrier side, so there's no way for them to tell if you've been blocked, making it less of a hassle for you.
Unfortunately on WhatsApp they can tell that you have blocked them, which is why it makes sense to just block their phone number and leave them on WhatsApp.
