If you're using CallControl at some point MacOS X will display a message like this to you:
This is, because CallControl tries to access your Contacts.app to get information about the people saved in your contacts/address book.
CallControl needs access to this information as it tries to identify incoming and outgoing calls for you. So CallControl will always try to find a contact for each phone number it gets from your PBX. Allowing CallControl to access your contacts will make using CallControl much more convenient for you as it won't show you phone numbers in the history, but pictures of your contacts and their name and type of phone number.
So, please click "OK" when receiving this message.