Train and monitor administrative personnel

It is your responsibility to institute proper personnel management techniques for allowing administrative user access to credit cards, site data, and so on.

You can control whether each individual administrative user can see all the credit card PANs (or only the last 4).

In most systems, a security breach is because of unethical personnel. So pay special attention the people you trust your administrative site with and to those whom you allow to view full decrypted and unmasked payment information.