I found the following notice at
http://support.qatarairways.com/entr...-reservation-:
Note for flights to and from the US: When you make a reservation through Qatar Airways Call Centre, at airport ticket offices, and city ticket offices or qatarairways.com one week or more prior to your flight departure, we will allow you hold the reservation for 24 hours without payment.
If you purchased your reservation directly with Qatar, it seems as if they have chosen to offer a 24-hour hold instead of 24-hour cancellation. However, if you purchased your ticket from a travel agent who doesn't offer the hold, then you can pursue a refund through that agent.