Open the Phone app
Tap Recents
Tap the info icon (i) next to the number you want to unblock
Tap Unblock this Caller
Confirm by tapping Unblock
Open Settings
Tap Phone
Tap Blocked Contacts
Swipe left on the contact/number you want to unblock
Tap Unblock
Open Settings
Tap Messages
Tap Blocked Contacts
Swipe left on the contact/number you want to unblock
Tap Unblock
Open Settings
Tap FaceTime
Tap Blocked Contacts
Swipe left on the contact/number you want to unblock
Tap Unblock