Don't want to receive messages from someone on WhatsApp? No worries, you can block that person.
Go to Settings > Account > Privacy Settings > Blocked Contacts. This page displays all contacts that you have blocked.
Press the button, then choose Block New Contact to select a contact you wish to block.
If you wish to block an unknown number that has sent you a message, you can select the chat of the unknown number, press the button, and choose Block.
That's it! You will not receive any more messages from those blocked contacts. Learn more about what happens when you block someone in this article.