KDDI Business Call Direct
Use au mobile phones as extension phones
––A collaborative function with office extension phones
Calling and receiving calls with an extension number
Extension calling is available between an au mobile phone and an office extension phone anywhere in Japan. No need to answer for someone else, take messages or call back.
Caller number notification and display 
The extension number of the caller is displayed on the receiving phone, making it easy to return the call by extension calling from the incoming call history.
- Whether extension number notification and display are available or not depends on the KDDI phone line type and the PBX model.
"SMS via extension" function
SMS can be sent/received using the same extension number as that for a voice call provided under the KDDI Business Call Direct service. This service is also available for workers who work in an office and don't have a mobile phone. These workers can send and receive SMS on a web site exclusively accessible from a PC after acquiring User ID to be linked to an extension number on a landline phone system.
KDDI Audio Conference Service Linkage Function
The KDDI Audio Conference Service can be used from au mobile phones subscribed to KDDI Business Call Direct by dialing an extension number.
Free numbering plan dial-in
au mobile phones can call individual extension phones connected to the office PBX.
Office extension phones that do not have dial-in numbers can also call au mobile phones directly using their extension number.
au extension call forwarding
By pre-setting the forwarding destination and forwarding conditions, incoming calls to an au mobile phone can be forwarded to another extension phone. Callers can be forwarded to the office pilot phone when you can't answer the call while on travel.
Self page function
Customers can check the details of their contract, check their usage fees, and change the extension number of an au mobile phone via a customer exclusive web page.
- A Self ID and password are required when logging in to the Self Page. For information about the Self ID and password (for first-time users), see "Getting Started (initial notification)".