I don't understand that. Example: you said to sell 1000 shares at $50. They sold the first 500 shares at $51 (the bid in the market at that time), then when the rest of the order didn't fill for a while, they sold the other 500 at $49? That doesn't seem right; I know my broker wouldn't sell any shares under $50 if I placed such an order.
Which broker did you use (so I know to avoid them)?
Seth