Open the Phone app
Tap Recents, Contacts, or Favorites
Tap the info icon next to the number or contact
Scroll down
Tap Block this Caller
Tap Block Contact to confirm
To block from Messages, open the conversation
Tap the contact name or number at the top
Tap Info
Tap Block this Caller
To block from FaceTime, open the FaceTime app
Tap the info icon next to the person
Tap Block this Caller
To manage blocked contacts, go to Settings
Tap Phone, Messages, or FaceTime
Tap Blocked Contacts
Tap Add New to block someone manually
Tap Edit to remove someone from the blocked list