Incoming calls shows as unknown

If there is no number displayed and instead it says “unknown” that means that your carrier is not providing caller ID to your phone. You need to call them. If it displays a number but does not display a contact name go to Settings/Phone and turn on Dial Assist.

Caller ID is a carrier feature. Contact your cellular carrier.

What format have you stored your contact' Phone numbers? Do not use any spaces between them spaces will allocated based on the country code that you provide.

Watch the GIF below the spaces are not entered by me.