Call directly to extension numbers in office from anywhere in Japan with a flat-rate calling charge
au mobile phones can call office phones by their extension numbers. Bases nationwide can also be connected by KDDI phones. This service offers flat-rate calling charges.
FMC Extension Solution that uses dual-use phones.
You can use the same phone as an extension phone in the office (office PHS/wireless LAN) and as an au mobile phone when you are out of office.