Find the contact you want to block, then tap the contact.
Here are a couple of alternative options for blocking a contact:
Open the chat with the contact, then tap the contact's name > Block Contact > Block or Report Contact > Report and Block, which will report and block the number.
Swipe left the chat with the contact in your Chats tab, then tap More > Contact Info > Block Contact > Block or Report Contact > Report and Block, which will report and block the number.
Block an unknown phone number
To block an unknown phone number, you have a couple options:
If this is the first time you've been contacted by that phone number, you can open the chat and tap Block > Block.
Open the chat with the unknown phone number, then tap the phone number > Block Contact > Block or Report and Block, which will report and block the number.
Note:
Messages, calls, and status updates sent by a blocked contact won't show up on your phone and will never be delivered to you.
Your last seen, online, status updates, and any changes made to your profile photo will no longer be visible to contacts you've blocked.
Blocking a contact won't remove them from your contacts list, nor will it remove you from the list on the contact's phone. To delete a contact, you must delete the contact from your phone's address book.
If you're concerned whether a blocked contact will know if you're blocking them, please read this article.
Unblock a contact
Tap Settings > Account > Privacy > Blocked.
Swipe left on the contact's name.
Alternatively, tap Edit > the red minus sign icon.
Tap Unblock.
Here are a couple of alternative options for unblocking a contact:
Open the chat with the contact, then tap the contact's name > Unblock Contact.
Swipe left the chat with the contact in your Chats tab, then tap More > Contact Info > Unblock Contact.
Note: If you unblock a contact, you won't receive any messages, calls, and status updates the contact sent you during the time they were blocked.
Related resources:
How to block and unblock contacts: Android | KaiOS