You probably didn't specifically inform them that it has a single hairline crack, so I recommend going into an Apple store and they'll swap it out per policy.
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Believe me, I tried to argue that with my Apple store manager sister to no avail. They set the policy so it doesn't matter what we think.
Actually I did inform he guy that it was a hairline crack and the phone was working normally as I was calling him with it. I see it posted everywhere and they still say that the cost for the repair is $109, but when scheduling the service I am still being charged $299 plus $6.95 shipping plus tax. No one can seem to tell me why. They just say that it is $109.
I fully own the responsibility of dropping my device and am willing to pay the $109 to get it repaired. But for $325, I'll just live with it.