It seems to me, that a phone 18 days old, has a small crack starting in top left corner and has never been dropped, would be covered by warranty. I just moved to Verizon on 3/6/2014 from Sprint. I was an employee with Sprint for 33 years and never had this kind of problem.
Took the phone into the Verizon store and was told it was not a warranty issue? I have the Mophie Juice Pack on it, bought at the same time, and no damage to the it and the case of the phone, as I never dropped it yet!
This is not the way to treat a new customer.
Ken