In order to block a number, you must first add that number as a contact. Once that number is a contact, you can block that number in-app.
- Select 'Contacts' at the bottom left of your screen.
- Click the contact that you'd like to 'Block'.
- Toggle the slider for 'Block Contact' to the right to block. The slider will be green, which indicates that the contact is now blocked.
If you decide to unblock your contact, you can simply toggle the slider back to the left, and it will no longer be green, indicating that the contact is no longer blocked.