What is your PSTN connection? Is it an FXO port on the router? If so, you use a 'connection plar XXXX' where XXXX is the number of the Auto-Attendant. If it's a PRI, you need to make sure that the main number gets routed to the CUE AA number (usually those will be the same, for instance, if your number is 2125551212, then you'll only receive 1212 from the carrier, which would be the AA number).