How to stop no caller id calls iphone

How do I block calls that say no caller ID?

Enter 000-000-0000 for the phone number. This should stop calls from calls that come from "zero" numbers. If you want to know who you are getting a call from when it says "Unknown Call" you can go to www.trapcall.com and sign up for their service.

Why do I keep getting no Caller ID calls?

When you see a call from “No Caller ID” appear on your screen, it means that the person who is calling you has stopped their phone number from being visible to you. This means that they purposely want to hide their contact information from you so that you cannot trace the call back to that person.