Where can trade my phone in for another?

well i just left the T-Mobile store and all they said was i can trade my in and see how much money they would give me but i want a whole other phone so no help... (looks away in disappointment) i have a Nokia Nuron 5230 and it has a few scratches but work perfect and has APPS and everything. It a good phone ( i just need some thing different) (shame) i'm looking for places in Dallas,TX.