Execution of orders

[JAC1390@xxxxxxx]

I know this may be off-topic but I don't know where I might find an 
answer.Any ideas appreciated

I entered four GTC orders to sell a stock @9.00, 9.25, 9.50 & 9.75.I sold the 
$9.00 stock and received a fill.Subsequently the stocks symbol changed and 
the stock traded as high as 10.50 bid.The brokerage firm,American Express 
claims that there is nothing done on these orders because I didn't change to 
the new symbol.

It has been my experience that the brokerage firm or the specialist or market 
maker who the brokerage firm entrusted the order is responsible.I don't know 
whether there is an actual quotable rule. 

Any Ideas???
JAC