Patent ID: 8126455

Claim:
A portable terminal apparatus that is connected to an operator through a communication line and is connected to an operator at a roaming destination through a communication line, comprising: a storing unit that stores operator information on the operator; and an information processing unit that requests operator information to a connected operator with specifying an area of the roaming destination, receives, from the connected operator, operator information on an operator having a service area thereof in the specified area, the operator information including any one of contents of a service provided using telephone communication as a medium, an area range, an area covering rate, the number of subscribers, a calling charge and a charging method, and registers the operator information in the storing unit, wherein before the portable terminal apparatus moves to the specified area, the information processing unit receives the operator information, selects an operator at the roaming destination from the operators having service areas thereof in the specified area, registers, along with trigger information, operator information on the operator at the roaming destination in the storing unit, the trigger information distinguishing a radio wave coming from the operator, and makes setting to receive services of the operator at the roaming destination, and after the portable terminal apparatus moves to the specified area, the information processing unit receives trigger information from the operator at the roaming destination, compares the trigger information registered in the storing unit to the trigger information received from the operator at the roaming destination, and changes an operator to the operator at the roaming destination.