A prepaid calling card, also known as a phone debit card, allows users to pre-pay a selected amount of charges for telephone services, generally, charges assessed for completing telephone calls. Later, when the user makes a telephone call or otherwise incurs charges for telephone services, the charges for the provided services are deducted from the value of the card. Pre-paid phone debit cards have become increasingly popular in recent years, particularly among travelers who wish to avoid the additional expenses incurred when using calling cards which bill charges to a designated telephone number or credit card. In addition, it allows the user to both carefully monitor usage and avoid the use of unknown long distance carriers, thereby preventing the user from receiving unexpectedly large telephone bills on his or her return home.
Generally, when purchased or otherwise acquired, a phone debit card contains a number of "call units". Call units are directly related to the value of the card. For example, a one-minute domestic long distance call may cost 1 unit while a one-minute international long distance call may cost 5 units. A typical phone debit card requires the user to contact a service provider, for example, by dialing an "800" or "888" number. The service provider will ask the caller to identify themselves, typically, by providing an account number printed or otherwise recorded on the phone debit card. The service provider will review a record for the identified account which is maintained in a storage facility to determine if the phone debit card has any remaining value. If the phone debit card has remaining value, the service provider will authorize the caller to make a telephone call. The service provider will then debit the identified account for the cost of making the telephone call.
Depending on the particular technique used by a service provider to deduct units from a phone debit card, it is entirely possible that a user or users of a card may consume more units than that originally credited to the card at the time of purchase. Furthermore, since the vast majority of phone debit cards are, in effect, bearer instruments which lack any identification as to the owner of the card and are often used at public terminals, once units in excess of the pre-paid value of the phone debit card are consumed, the service provider rarely has any way of recovering the value of the additional telephone services charged to the card.
To reduce the potential for fraudulent use of telephone debit cards, some service providers has built certain restrictions into the use of their debit cards. For example, some service providers effectively prohibit multiple simultaneous users on one account by refusing, once a first user of an account has been authorized, to authorize use of the account by a second user until the first user has completed their call. However, permitting multiple simultaneous users of an account is a popular feature of phone debit cards. As a result, service providers who prohibit such uses risk losing sales to those service providers who sell phone debit cards with this feature.
In one existing technique, the user purchases, from a service provider, a phone debit card having an account number to which a specified number of call units have been credited. Later, the user dials into a switch operated by the service provider from which the user had purchased the card. The service provider searches an external database for the account. If the account has unused call units, the number of unused call units are copied from the external database to the switch. The switch then authorizes the user to begin a phone call which may continue until the user releases the call or all of the copied call units have been consumed. As the call continues, the switch will reduce its record of the number of call units remaining for the account and, when the call is released, the switch will update the external database as to the number of call units remaining for the account.
The foregoing technique also allows multiple simultaneous users of a single account. Because of this, there exists considerable potential for fraudulent use of an account. When a first user attempts to use the account, an indicator of the amount of remaining credit for the account is copied to the switch. However, the database continues to reflect the same amount of remaining credit. Thus, if a second user accesses the same account before the first user terminates his or her call and the database receives an updated value for the amount of remaining credits, the database will again advise that the account has the indicated number of credits, even though the same credits have been authorized for use by the first user. Thus, if both users consume all of the credits for which the database has authorized the switch (or switches) to allow the callers to use, the callers will have collectively used more credits than those remaining on the debit card.
Nor is fraud the only process by which the foregoing technique may cause the service provider to suffer losses. As previously stated, the external database copies the number of remaining call units to the switch and, when the call is completed, the switch will update the external database as to the number of remaining call units. If, however, the connection between the switch and the external database is lost while the call is continuing, the switch will be unable to update the external database. Since the connection between the switch and the external database is entirely separate and distinct from the connection for the call itself, the call may continue after the switch and external database have been disconnected from each other. As a result, therefore, the user may consume some or all of the remaining call units while the external database will continue to indicate, as the number of call units remaining, the original number of call units. This permits the user to consume more call units than that originally provided by the phone debit card.