How do I block no caller ID calls on iPhone?

To block calls with no caller ID on your iPhone, you can enable the "Silence Unknown Callers" feature:

1. Open Settings.
2. Tap Phone.
3. Select Silence Unknown Callers.
4. Toggle it on.

This will silence calls from numbers not in your contacts, sending them directly to voicemail.

Alternatively, you can create a contact named "No Caller ID" with the number "000-000-0000" and block this contact:

1. Open the Contacts app.
2. Tap the "+" icon to add a new contact.
3. Enter "No Caller ID" as the name.
4. Enter "000-000-0000" as the phone number.
5. Save the contact.
6. Go to Settings > Phone > Blocked Contacts.
7. Tap Add New and select the "No Caller ID" contact.