Open the Phone app
Tap Recents, Contacts, or Voicemail
Tap the info icon next to the caller
Scroll down and 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
Tap Block Contact to confirm
To block from Contacts, open the contact
Scroll down and tap Block this Caller
Tap Block Contact to confirm
To manage blocked numbers, go to Settings
Tap Phone, Messages, or FaceTime
Tap Blocked Contacts