I want to trade in my iPhone 4 for a Samsung Galaxy s4, how can I do it?

I just got my iPhone 4 a few months ago. It still looks pristine; no scratches, scuffs, or anything. If I went to Radioshack or Best Buy or something, is there any way I could get the brand new Samsung Galaxy s4 if I traded my phone in or something?

U cud, but ud havr to do a cintract with a deposit or pay for the upgrade upfront

How much would I have to pay