Does your itinerary involve other airlines? Are you flying within 7 days? If so, there is no hold option. You are allowed to cancel with 24 hours though. This has been the policy for some time. There are a number of threads on this subject.
http://www.flyertalk.com/forum/ameri...xed-metal.html
http://www.flyertalk.com/forum/ameri...r-hold-22.html