Android. Contacts.
Deleting contacts
WhatsApp quickly and easily recognizes which of your contacts are using WhatsApp by accessing your phone's address book. To delete a contact, simply delete their phone number from your phone's address book:- Open WhatsApp and go to the Chats tab.
- Tap the new chat icon > Tap the contact > Tap the name at the top of the chat screen.
- Tap More options > View in address book > More options > Delete.