Open the Phone app
Tap Recents, Favorites, or Contacts
Tap the info icon next to the number or contact
Scroll down and tap Block this Caller
Tap Block Contact to confirm
Open Settings
Tap Phone
Tap Blocked Contacts
Tap Add New
Select the contact to block
Open the Messages app
Open the conversation with the number or contact
Tap the contact name or number at the top
Tap Info
Tap Block this Caller
Tap Block Contact to confirm
Open Settings
Tap FaceTime
Tap Blocked Contacts
Tap Add New
Select the contact to block
Open Settings
Tap Phone
Tap Silence Unknown Callers
Turn on Silence Unknown Callers