If you book an "insider fare" on amextravel.com and pay with your points you will get free changes on AA ($39 phone fee applies per passenger)
If you want to pay in cash you have to call to get the insider/private fares... some agents know how to do it, others dont. You will have to pay $39 per passenger if you book this way. I'd only do that if you know there is high potential to changing your flight.
Also, if you apply an SWU or upg with miles on one of these fares it makes it very difficult to change. It becomes an AMEX vs AA battle and can be very frustrating as AA takes "control" of the ticket when the upgrade is applied yet they still defer to AMEX for changes and AMEX defers to AA.
I have used this perk a few times and it is nice to have.