If you find that the caller ID is not displaying even though you have a caller stored as a contact, then these simple changes to your settings will help.
1) Go to iOS Contacts. search for 'Another Number' and delete the contacts that appear in the list. Then reopen the Another Number app.
2) Go to iOS Settings > General > Background App Refresh - Make sure this is turned ON. And Another Number app is enabled.
3) Go to iOS Settings > Another Number - make sure everything under 'ALLOW ANOTHERNUMBER TO ACCESS' is enabled.
4) In the app itself, go to More > Receive Calls > Set to 'Try both'
If you are still having problems after this please contact out support team who can look into this for you - firstname.lastname@example.org