Open the Phone, Messages, FaceTime, or Contacts app
Find the person you want to block
Tap their name or number
Scroll down and tap Block this Caller
Tap Block Contact to confirm
To block from Settings, open Settings
Tap Phone, Messages, FaceTime, or Mail
Tap Blocked Contacts
Tap Add New
Select the contact you want to block
To unblock, open Settings
Tap Phone, Messages, FaceTime, or Mail
Tap Blocked Contacts
Swipe left on the contact
Tap Unblock