You can use dial-peers as an alternate solution. For example, if you want to use 12345 as your FAC and your normal dial-peer is something like this
dial-peer voice 10 pots
destination-pattern 9T
port 1/0/0
Change this dial-peer to
dial-peer voice 10 pots
destination-pattern 123459T
port 1/0/0
Users would need to enter the FAC followed by the DNIS to place calls.
Regards,
Anup