Almost every airline will let you cancel within 24 hours no questions asked. However, USAirways decided to change its own policy some time ago to not be so customer friendly. They originally agreed to this in 2000 after the DOT wanted to have a bill of rights.

I made a similar mistake and within an hour realized it. I called them and they wanted to charge the fee. I pointed out that on their website it seemed to indicate I could cancel without penalty. After getting a supervisor and clearly stating I just make the reservation within the hour, they should cancel the ticket. They did, but it took some fighting. What a hassle. Other airlines are much better about this.

http://www.usairways.com/awa/content...rviceplan.aspx

Allow reservations to be held or canceled

Each airline will allow the customer either to hold a telephone reservation without payment for 24 hours or (at the election of the carrier) to cancel a reservation without penalty for up to 24 hours, in order to give customers an opportunity to check for lower fares through other distribution systems, such as travel agents or the internet.

US Airways will hold a customer's reservation without payment or penalty for a maximum period of 24 hours. This policy applies to refundable as well as non-refundable fares.

A telephone reservation is defined as an itinerary or trip for which payment has not been received. Purchased, refundable tickets (paper or electronic) will be refunded via the US Airways refund department regardless of when the tickets were purchased. Changes made to the itinerary after purchase will be assessed the current change fee regardless of when the tickets were purchased.