There are several ways to block people on your iPhone. You can do it within the Settings app, or the Phone, Messages, and FaceTime apps. The Settings app usually works best if you already have the persons contact details in your Contact book.
1. Tap the Settings app and then tap Phone.
2. On the next screen, select Blocked.
3. Tap Add New…
4. From the Contacts screen that appears, tap the name of the person you want to block.
5. All the ways that person can contact you (email and phone numbers) will be added to your blocked list.
You can also block random phone numbers you get calls and texts from:
6. In the call log in the Phone app tap the “I” info button by the number you want to block. Alternately, in Messages, tap the “I” info button under the Contact button in the text you receive.
7. On the Info screen, scroll down and tap Block This Caller.
To unblock people you have blocked:
8. Tap the Settings app and then tap Phone.
9. On the next screen, select Blocked.
10. Tap the Edit button.
11. Select which numbers and emails you want to unblock and tap Unblock.