You did indeed fall victim to a shady store, intenionally or unintensional There are many of these questionable stores in the confines of NYC. What you bought was a copy, AnyDVD indicated that when it showed it was region free.
I don’t understand why you paid 20.00 for a 15.00 movie, either the 20.00 figure is not correct or you need to use better judgement in the stores you buy from. Any reputable business would never ever put something like that out for sale. One look around these type of stores should alert you what is going on.
In could very well be the details you provided are true and you just didn’t know any better, in any case I would bring the DVD back and demand a refund and tell the clerk you are calling the police unless refunded. I’d still call the Police after the refund because they are still crooks no matter how you look at it.
I must admit though I feel you paid far less then what you are stating and may not follow up on my suggestion.