How To Block Calls From Anyone Who Isn’t On Your iPhone's Contact List

Follow the instructions below for your particular phone to block calls from unknown callers. 

To block unknown callers with an iPhone if it’s running iOS 13:

1 – Tap Settings.

2 – Tap Phone.

3 – Scroll down and toggle the Silence Unknown Callers setting to On.

To block unknown callers with an iPhone if it’s running iOS 12 or earlier:

1 – Tap Settings.

2 – Tap Do Not Disturb.

3 – Tap the slider switch beside the“Manual” setting to enable it.

4 – Tap Allow Calls From.

5 – Select All Contacts.