How do I block or unblock a contact?
You can prevent a contact from sending you messages by adding their phone number to your Blocked list. To learn more about the effects of blocking a contact, see this article on blocking contacts in WhatsApp.
On iPhone, there are two ways to block a contact:
Use the Block button which is displayed when you get a message from somebody who is not in your address book:
Go to WhatsApp > Settings > Chat Settings > Blocked, then tap the Add New button to add contacts from your address book to your block list.
To unblock a contact, open the Blocked list with the above steps, slide your finger to the left on the contact you wish to unblock, then tap the Unblock button.
WhatsApp Support Team