First of all, good luck. Sony does basically the bare minimum legally required, which means in the US you get less customer rights than in the EU.
If it's a game and you bought it within the last 14 days and you haven't downloaded it, then you should be able to get it. Otherwise, it's going to be tougher. People used to say they'd give you either one refund ever or maybe one per year, with Sony calling it a "one time thing because we value you", though perhaps with their updated policies that's over.
Word of warning. If using their live chat support and you don't like the person you're dealing with, and you try again to get someone else, they can stealth ban you. What happens then is you'll enter your info to start the chat and it will take you to a page saying their site is down and try again later, but if you enter different user info it works, which is a really dick move of them.
