If the person is saved in your contacts, you can unblock them directly from their contact card.
If you’re not receiving calls from someone you thought you unblocked, also check: unblock blocked calls iphone
Use this method if you have a recent call log from the number you want to unblock. If the person is saved in your contacts,
Tap the blue "i" icon next to the number you want to unblock. unblock blocked calls iphone
After unblocking, calls from that number will no longer be blocked, and you will receive their calls and messages as usual.