How to block contacts
Blocked contacts will not be able to send you messages or call you. If someone is bothering you, you can block the contact.
1. To block a stranger you haven't added as a contact, open the chat sent by unknown contacts > click "BLOCK" at the top
2. To block a friend from your contacts, tap the friend's profile picture > tap their profile picture again > go to their profile page > Block.
If you want to unblock someone, go to [Me] > Security & Privacy > Blocked Contacts > Find the contact and tap UNBLOCK.
After this, he will be removed from the blacklist.