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 the contact from your phone's address book.

To delete a contact:

1. From your phone's home screen, go to People.
2. Tap and hold the name of the contact you wish to remove.
3. Select delete from the menu.

If you do not want someone to be able to message you on WhatsApp, you can block that contact.

Learn how to delete a contact on: Android | iPhone