I bought a tmobile sidekick from craigslist that doesnt work am i entitled to a refund?

[Edward]

I recently bought a sidekick for tmobile and the guy specifically told me it was in great condition i brought it home and tried 3 chargers and didnt charge and when i finally turned it on i put in my sim card and it doesnt read my sim card i called him back and he answered and hung up and called me later saying it worked when he had it and that i did something to it myself to cause it to not work and that he wont give me a refund what should i do about it