I purchased Amnesia (game) from the Ubuntu Software Centre. It crashes on startup every time and I therefore want to return it for a refund. I can't find a way of doing so through the USC and, strangely, I can't find any trace of this having been asked before (maybe bad googling on my part). So the question is: how do I return a purchase and get a refund through the USC?

EDIT
Installing proprietary driver for AMD catalyst fixed Amnesia, but I still think this is an important question because it's basic customer service for any purchase. I'd therefore appreciate any answers anyone can find and I will continue to look too. If I find the answer I'll post it here.