You can add tags/notes to numbers without saving them to Contact. This allows you to find out quickly through search box and view the caller’s information when they call without having them listed in Contact.
1.Launch the Phone app and tap Recents.
2. Tap a phone number → ( i ).
3. Tap Add tag/note, enter a tag, and then tap Add.
When a call comes from that number, the tag/note will show under the number. Screenshots below...