If you already have an gold iPhone 5s, can you exchange it to get a different color?

If you already have an gold iPhone 5s, can you exchange it to get a different color?

I got my gold iPhone back in march?(So my 2 year contract isn't up yet.) When i went to go get it the guy didn't really give me a choice of what color So i just went with it, because at the time i liked it. Now that I've had it for awhile I'm not that happy with it. Also its got a few dents. Not a lot though. Anyway I was just wondering if i could go back to At&t and Get a different color? And if so, i know it may cost some money.