sorry, must be an old link.
If you wish to use a different language other that the default American English that comes with Asterisk,
Create a subdirectory for the particular language (eg: ‘au’ for Australian English, ‘fr’ for French, ‘it’ for Italian etc.) in the /var/lib/asterisk/sounds directory, e.g. /var/lib/asterisk/sounds/au and send all your prompts sound files there. Also create the language directories in the digits, letters etc directories, and send the entire prompt files there.
Add the following line in the iax.conf and sip.conf configuration file under [general]. In zapata.conf configuration file the line should be added under channels].
language=au ; (or fr, it or whichever language is installed)
Next: put "fr" (no quotes) on the extension's language field