They probably can't just change the order. They probably have to refund original and recharge you for the *technically* different game.
Granted, an intelligent cashier would just refund to a gift card and then recharge that gift card with all your same info, but, meh, they are minimum wage kids working there typically. Not the brightest.
(That is not a slam on ALL Gamestop employees, just a statement of observation that most are teens that generally aren't all that bright when it comes to real world problem solving)







