LAFNAC DIGITAL COMPUTERS Liars and thieves New York, New York

This store put me in such a bad situation, im from Brazil and I went into their store to buy a cell phone
the guy who was selling to me offered me a cell phone but he also convinced me to buy a lot more of things saying that he would do it in four payments, so I as not going to pay for the entire 1333 dollars at once but I would pay only 333.25 per month for four months, so I was ok with it, but then they rip me off 799,99 at once from my credit card and then some amount that he was saying was going for the next month they rip me off again 533 dollars, so my credit card limit was off, I couldnt afford to buy any food, and was left to eat one slice of pizza for the day. So I went in the store to complain and the guy lied on my face saying that was going for next month (what a b*****d) and lied in my face about the first amount they took it (799,99), anyway he give a refund for the 533 dollars, i give some stuff back, but what I want was to give everything back except my cell phone (what I wanna to buy in the first place) and receive a refund for that, but wont give to you. I feel very bad to be treat like this, in my country we have problems but things like that never happens,  at least there  you  know who are the bad guys, but once you go into some eletronic store in NY you dont expect to be ripp off the way I was, im looking for help I want to know what can I do to stop this bastards from doing what their doing, there must be some justice in this country.