No, SU is completely weird about returns. If you want to return something you can only exchange it, and if you exchange for merchandise over the amount of the merchandise you are returning, you have to give them your credit card info on the return form. If you return it for less, you lose the difference. They don't issue credits.
Don't you think that's odd? I mean about losing the difference? I do.
So the game you have to play is to try to make up an exchange order that is as close to the original as possible without going over. Or be willing to pay the overage. I'm not so averse to paying an overage, but I don't really feature writing my credit card number on a form and putting it in the mail. But that's me. Probably no one else would give it a thought.