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You can set your phone to ignore calls from unknown phone numbers which are not saved in your address book. When you get a call from an unknown phone number, it will be diverted to your voicemail and is shown as a missed call on the call list.
1. Find "Phone"
Press Silence Unknown Callers.
2. Ignore calls from unknown numbers
Press the indicator next to "Silence Unknown Callers" to turn on the function.
3. Return to the home screen
Press the Home key to return to the home screen.