PURPOSE: To confirm a telephone call arrived while not attended and to take proper correspondence by displaying a caller name of a phone call arrived in a virtual extension on a multi-function telephone set and recording a history automatically even when the telephone set does not reply so as to retrieve the recording after a personnel in charge or the like returns its company.

CONSTITUTION: A private branch of electronic exchange 4 accommodating a multi-function telephone set 3 is combined with an information processing unit 1 having a management file section 2. A different virtual extension number is set to a specific customer and it is registered in a virtual extension number table 41 and a virtual extension number is informed to the customer in place of an extension number. An incoming call arrived in the virtual extension number is transferred to the transfer destination extension number by allowing a virtual extension transfer means references the virtual extension transfer table 42. A caller information management means 11 references a caller management file 21 to obtain a caller name from the virtual extension number and displays it on a multi-function telephone set 3 being a transfer destination and stores the incoming call information via a history information management means 12.