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I'd just give them some story about how your proximity sensor isn't working. They are less likely to check the problems than an apple store. Anyway, that's how I'd play it.
 
I returned my 32GB to get a 16GB, and I don't recall them even looking to see if it was in the box. I don't think you'll have to worry about it.
 
Tough to Say.

I know when I returned my first 2 iphone 4's at Apple they didn't look it over all that much. In fact the whole thing was very informal. They didn't even ask for a receipt the first time. Then again it was right after the "problem" was announced. Did you get a full subsidy? If not, and you paid over $400 for it you will have to wait for a check refund. Pretty sure they don't do cash returns for over $400. (I returned a TV once only a week after I bought it) The check came in a week or less.

I don't know how far you are from an Apple store but if it's within an hour I'd go there. They made it very painless for me. Then again I was replacing not returning. Good Luck.

Blonde Buddhist
 
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