So, lesson learned: don't change your shipping address on a future shop order that's already shipped an item.
One of my E3 orders last year was W101, Mario Kart and FExSMT (hey, it was there). Obviously the latter two haven't shipped yet but I moved a few weeks ago and the website wouldn't let me change the address. I called them up, the guy changed my address and everything was fine.
Fast forward to today, I check the order to see if MK8 has shipped and my shipping address has reverted to some weird-ass combination of my two shipping addresses. New address, but old postal code and city. And then the guy I called says they can't change my shipping address, which makes no sense because that's the whole reason it got screwed up.
He said he could only fix it by cancelling the order and flagging my 'notes' for a $20 discount, which is fine I guess but the game's price has gone up $5 since last E3. Should have just let it get sent to my parents' place and had them mail it here.