Haha, that's pretty big mistake. It's always awesome when stores wind up sending the wrong items. I'd still return it out of principle. Not to be like a goody "they me the sent wrong item, silly them. here, have it back!" person, but moreso because they made a fucking mistake. You asked for item A, they should send you item A. Make them acknowledge their mistake. You'll either come out getting your two R4's after everything, or, you may even come out on top because if they want to keep their customers happy, they'll reimburse you for the mistake when it's corrected.