OP,
I am also from Venezuela and I understand your problems. We don't have any system that works over here and we are very hesitant to trying and trusting warranties. It sucks.
That said, in my time in the US, I have learned that Apple is top of the line when it comes to doing right for their customer. Call them and find out what they can do.
The only thing that worries me is that the phone is from T-mobile locked and you bought it from a third party (Venezuela for ripoff) they probably bought the phone from T-mobile under contract and didn't pay therefore the phone is blacklisted in the US. Every phone sold in Venezuela is almost always in this bucket unless you buy straight from the carriers.
However the worse thing that can happen is they will take the serial number over the phone and tell you they can't do anything because the phone has been reported "stolen".
No hay tiempo que perder. LLAMA A APPLE.