Calling card fraud results in millions of dollars of illegal charges each year. Although users are generally not liable for fraudulent calls, it can be very frustrating to argue about charges with the carrier.

In many cases, only the account number is stolen. Vandals "shoulder surf," memorizing the numbers they see punched in by a user. To avoid this kind of theft, try to block the phone when entering your account number.

In addition, make sure to disconnect from the carrier before leaving the phone. Otherwise, the next user can continue to charge calls to your card.

Toll restriction allows a company to block calls to certain area codes or dialing exchanges. This minimizes your exposure to theft by denying thieves the ability to reach 900 numbers or overseas locations.