Open WhatsApp
Go to the chat with the number you want to block
Tap the contact name or number at the top
Scroll down and tap Block
Tap Block again to confirm
To block from a chat list, open the chat, tap the three dots, tap More, then tap Block
To block from WhatsApp settings, go to Settings
Tap Privacy
Tap Blocked contacts
Tap Add
Select the contact or enter the number to block
To block an unknown number, open the chat
Tap the number at the top
Tap Block
Tap Block again to confirm