Whatever you do, don't put your phone in the freezer.
Not even for a few minutes. You have to realize that if you
don't do what the company recommends, then they can give
you a hard time. If they find out that you put
the phone in the freezer, they can use that against you since it's not in the their troubleshooting documentation.
The best thing to do if it's been less than 30 days is to return it. As you can see, there's nothing unusaul about some of these units having this border problem and that should be enough for them to give you one that doesn't have it.

As mjorange pointed out, this is all the reason why everyone should get the $4/month replacement program on their account. Keep in mind though, that there is a $35 deductible.

One other note, if you try to sign up after you activate your phone, then there's like a 20 day waiting period before it goes in effect.