The thing to know about AAA rates/discounts is you CAN apply a discount to ressie that has already been made. AAA discounts are generally available when WDW sets rate for the next calendar year (typically the summer previous). There are a limited number of discounts available so the best advice is to reserve early, ask for the AAA discount, or as this poster found, keep asking (somebody with one might cancel). Busy periods or short timelines might not get a discount but it can't hurt to try.
Bama ED
PS - the number to call for ANY single ressie is 407-WDISNEY. You don't call the Fort per se.