To block a number, from the home screen select the Phone app.
Note: You cannot block an Unknown Caller (No Caller ID), but you can turn onDo Not Disturbmanually and set it to 'Only allow calls from your contacts list'. The call blocking feature may not affect phone calls made or received via third party apps installed on your device. Please contact third party app developers for assistance with such applications.
Select the Info icon next to the contact or phone number you want to block.
Scroll to and select Block this Caller.
Select Block Contact.
To unblock, select Unblock this Caller.
To see blocked contacts and phone numbers, from the home screen, select the Settings app > scroll to and select Phone > Call Blocking & Identification.
To add a new blocked contact, select Block Contact... then select the desired contact. To unblock a contact, select Edit > select the delete icon next to the desired contact > Unblock. Select Done when finished.