PURPOSE: To eliminate the need for the service re-setting by manual operation of the user and re-dialing by discriminating a cause to an incoming call rejection with respect to the incoming call rejection from a called ISDN terminal equipment and selecting automatically the service and implementing re-dialing.

CONSTITUTION: When the user of a subscriber terminal equipment 27 connecting to a caller ISDN terminal equipment 21 sends data of the packet service from the terminal equipment 21 and receives an incoming call reject from a called ISDN terminal equipment 22 because of different service, the terminal equipment 21 uses an analysis section 24 to discriminate a cause to rejection. Then a service changeover section 25 selects the line exchange service automatically and a re-dialing section 26 makes data transmission in the service form after the changeover to the terminal equipment 22. Thus, it is not required for the user to manual-service re-setting and redialing for the data communication and then the service performance is improved.