To block unknown callers on your iPhone, you can use the built-in feature called Silence Unknown Callers , available on iOS 13 and later. This feature automatically silences calls from numbers that are not in your contacts, recent calls, or Siri Suggestions, sending them directly to voicemail without ringing your phone. These calls still appear in your recent calls list, so you can check them later if needed.

How to Enable Silence Unknown Callers

1. Open Settings on your iPhone.
2. Scroll down and tap Phone.
3. Find and tap Silence Unknown Callers.
4. Toggle the switch to turn it on.

Once enabled, calls from unknown numbers will be silenced and sent to voicemail, while calls from your contacts and recent callers will come through normally

Additional Options to Block Specific Numbers

• To block a specific known or unknown number, open the Phone app.
• Go to the Recents tab.
• Tap the Info (i) button next to the number you want to block.
• Scroll down and tap Block this Caller.
• Confirm by tapping Block Contact.

This blocks calls, messages, and FaceTime from that number

For Calls with No Caller ID

You cannot block calls that show as "No Caller ID" directly. However, you can use Do Not Disturb mode to allow calls only from your contacts:

• Go to Settings > Focus > Do Not Disturb.
• Customize it to allow calls only from your contacts.
  This way, unknown or hidden numbers won’t ring your phone

Using Third-Party Apps

You can also install third-party call blocking apps from the App Store that help identify and block spam or unknown calls. After installation:

• Go to Settings > Phone > Call Blocking & Identification.
• Enable the app to allow it to filter calls

In summary, the most straightforward way to block unknown callers on iPhone is to enable Silence Unknown Callers in Settings > Phone, which sends unknown calls to voicemail silently. For specific numbers, block them individually via the Phone app. For calls with no caller ID, use Do Not Disturb settings to allow calls only from contacts. Third-party apps offer additional spam blocking capabilities if needed.