They have requirements for a FULL refund: Items must be in new condition , Items must be returned with all original packaging and accessories , Media items (for example, movies, music, video games, and software) must be unopened and still in their plastic wrap ,Musical instruments, televisions, and consumer electronics must have a UPC or serial number ,Shoes and clothing must be unworn. If you have not followed the above conditions, they might provide you a partial refund or it really depends as well with the reseller. You need to contact the reseller first and ask for details.
You'll need to check the specific seller's policies, but in most cases if you don't return all the items that came with the package, then you won't get the refund. You don't get to keep parts of it for free, it's an all or nothing deal.