To provide a method for charging pluralities of calling cards by which the convenience of use of prepaid calling cards is enhanced and a network resource is saved.

The method of this invention imposes charging on pluralities of calling card accounts in a signal call by an operator service system OSS 102 automatically. The OSS 102 confirms validity of pluralities of received calling card accounts and decides a maximum calling time. Before the balance of all the calling card accounts given to a caller runs out, the caller is informed that the balance will soon be zero, and then an option of paying the tariff for the present call on another calling card account is given later. While the caller makes a substitute paying arrangement, the network resource is maintained. After a prescribed time, if another paying arrangement is not made, the line is interrupted and the network resource is out of use.