how to block calls from callers not in Contacts?

1. launch Settings App.
2. Turn “do not disturb” on Manual.
3. Only allow calls from your contacts list.
4. Also do not allow repeated calls with in 3 minutes to get though.

Or:

1. On your iPhone navigate to recent calls. Then get that call info. Use the copy feature on “Unknown Caller”.
2. Now go to contacts. Click the + sign to add a new contact. Use the paste feature and fill the fields like first name, last name, company and phone number. Press done.
3. Now you have option to block the caller.

Or: Copy UNKNOWN and paste it into blocked caller list. No number entry required.

Or:

1. Download a silent ringtone. Set this tone as your iPhone default ringtone.
2. Then go to My contacts and set the different ringtone for your contacts.
3. So now “number unknowns” call do not ring.

Your welcome