If the problem is with the phone itself, you can return it. You may not be able to return it to the same place where you got it first time but you can go to the T-Mobile Corporate store and get a new one if the problem really exists but you'll get the same phone in return.I recommend you to use the same phone for some months and once you'll be eligible for upgrade i.e after 11 months, you can go for another.If I were you,I'd do that but its up to you.