Open the Phone app, Contacts app, Messages app, or FaceTime app
Find the contact you want to block
Tap the contact name or info icon
Scroll down and tap Block this Caller
Tap Block Contact to confirm
To unblock, go to Settings
Tap Apps
Tap Phone, Messages, FaceTime, or Mail
Tap Blocked Contacts
Tap Edit or swipe left on the contact
Tap Unblock or Delete to remove the block