UNKNOWN NAME Showing up instead of actual phone number
The cell phone carrier sends this information, so I would do in order:


check for carrier setting update
Check for iOS update
Test with a couple numbers (delete the number from contacts if needed)
If it’s systematic, restart the device and update it. 
If it’s not systematic, call your carrier for support. 


In the end, carrier support may be needed to validate why this happens if it’s not a simple need to update or restart and retest.