Check this using the phone bill. This should serve as a deterrent to unauthorized calls and give you more information about phone calls for commercial reasons. Keep a close eye on the numbers posted month after month. Make sure there is a business reason for accessing these repeat numbers. Regardless of what your policy is or how much you are trying to control them, employees will likely use your devices from time to time for personal use. The best way to deal with the inevitable is to allow a reasonable amount of buffer noise, but to be consistent and vigilant in developing and enforcing the rules to ensure that personal use does not become excessive. Some companies also place the directive on recording screens that are displayed every time the computer is turned on to prevent employees from using their devices in a personal capacity. Personal use of devices that do not affect work is one thing, but how to deal with situations where the employee plays computer games during working hours (or does another type of personal business). Your equipment and the habits of your employees will guide your management of personal use situations.