i went to the store to return it, however the store owner claimed that they can't take back hardware, which i find hard to belive (anyone happen to know the legal bindings of the branch intertoys?). beside that they firmly claimed that the club nintendo code could never have been used before, and that they didn't had resold or patched the console, which i find really hard to believe because the version was 7.1 which came out in 2014, while ther is a 2013© on the box.
Maybe one of the employees took it home to play a game, 7.1 is indeed way too new. In Canada, 3DS XLs come in a box that have one round transparent sticker on one side of the box, 2 same stickers on the side you're supposed to open it. Did you examine those before buying? If you paid full price for a new product, you should insist you get a new product, not an open box one. The store I got it from (which is a drugstore) warned me in advance that any issues would have to be dealt with through Nintendo, as they wouldn't take it back, but I was allowed to carefully examine the box.
If I were you I'd worry about getting a 4.5 or lower first, if that store still has one, then when that is done, offer them to settle with you in regards to the first one and give you a nice discount, or you call/email/fax Nintendo Netherlands, give them your proof of purchase (slip), and your code, and ask them to investigate. If there are multiple complaints, perhaps Nintendo won't let them sell their products anymore.