Bought an iphone 4s unlocked and it doesn't work?

Bought an iphone 4s unlocked and it doesn't work I'm not mad because it costs about 700 and I only paid 390 but I'm just wondering is there anyway I can go to sprint or at&t and get a new data plan / sim card for it? I also need a replacement slot tray for the micro sim card because clearly its not the original its one bought to make the iphone unlocked.

I would bring it to the store and try for them to fix it, if they can't fix it I would sell it.

Sprint or AT&T won't help you with this as you're not the person who bought it from them. You can get the SIM tray from them. What you need to do is get the phone factory unlocked so it works with any GSM carrier like AT&T. You can mail this person (arghyle@rocketmail.com) who can help you with factory unlocking and anything you need.