The data amount of department counters stored in a database is reduced. In department counter information, departments with their data not having been updated in a predetermined period are set as ineffective departments so as not to register these departments in the database. This allows a reduction of department counter data maintained in a central control device because only effective departments are registered in the database. The validity of effective department/ineffective department classification is determined by comparison with the value of charge counters acquired along with the department counters.