To block specific numbers, select Block numbers. To view blocked messages, select Blocked messages. Note: For this demonstration, Block numbers was selected.
Enter the desired phone number, then select the Add icon.
Note: Select Inbox to block a number from your messages inbox. Select Contacts to block a number from your contacts.
To remove a number, select the Remove icon next to the desired number you would like to remove.
BLOCK UNKNOWN NUMBERS: From the Call settings screen, select Block numbers then select the Block unknown callers switch.
Note: To access the Call settings screen, from the Home screen select the Phone app > Menu icon  > Settings.