I have purchased many airline tickets through Travelocity and have always been able to change flight plans with an additional fee if my travel plans changed. In February of 2006 I purchased a last minute deal package for my wife and son. My son had a medical emergency ( his appedix ruptured and he was hospitalized for 5 days) and my wife and son were not able to make the trip.
I called several days in advance to cancel the reservations and was told that I would receive no credit as packages purchased through their last minute deal were nonrefundable, nonchangeable, and nontransferrable.
This information is hidded on their website under the FAQ section and clear down in their reservation confirmation just above the advertising section. It is not even anywhere close to the actual airline reservation.
So beware of any last minute deal, you can not get any credit at all if you have any change in travel plans.
I paid Travelocity 554 and they provided me nothing in return. After calling customer service I get dropped after being on hold anywhere from 12 hour to over an hour.