samsung blackjack problems

Samsung Blackjack 1 record?
I have a Samsung Blackjack 1 and has the problem has declined to appeal and I read that is a reminder about of them and you can call att and they replace for free. But my problem is I bought the phone used 3 months ago and I use tmobile on me, so I still can obtain the withdrawal or not and if I do I call?
If you use an unlocked phone to another carrier AT & T can not assume responsibility. You better call Samsung directly.