They will give you a gift card, or you will need to wait 24 hours and return and re-ring the transaction.
Web orders have a lag in the system that does not allow for adjustments immediately after purchase. It normally takes 90 minutes, but tomorrow's not a normal day for the system.
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How would that work out if I needed to apply rewardzone certificates (I forgot I even had them when I ordered), so ideally I'd like to go pick it up and have it rung up with the new amount (after certs deducted). I guess worst case if I have to go back the next day (I imagine I still get to take the phone with me, and just come back and do it as an exchange, or whatever), that would hopefully work..
That's exactly how it will go down. Will need to be a revisit to the store.
Let's say, you said I don't want the item, they will cancel the order and refund your money. However, the phone itself will not be able to be sold because the serial number is suck in limbo for that (normally) 90 minute period, but I suspect longer due to the overload.
So it's not you personally, it's just the way the item is sold and logged.