I may be wrong, but most airlines now give you 24 hours to cancel, they don't tell you this, but I think it is something Congress required of them. If you get within the 24 hours of the purchase, you may be able to cancel the higher priced ticket and buy at the lower price. I am pretty sure of this. I know DL has the policy, but I think it came about as a law when Congress was really grilling the airlines about their poor customer service a few years ago.