Order cancellation

I placed order last week and got a message today that said the order would be delayed again (until sometime in January).  I called to modify (buy a more expensive in-stock camera) and after indicating to the representative which camera and when it would be delivered, she cancelled my order.  She then told me that the credit on the order would only be the amount that was to be charged on my credit card and that should showed no recorded of the Dell coupon code that was used to bring the price down from $570 to $220.  She then blamed me for not telling her that I used a Dell coupon for the order and transfered me to another department.  After sitting on hold for a total of an hour and being bounced between representatives I hung up.  Online chat simply referred me to the FAQs online and gave me the same phone number to call again.

Can someone tell me how I can get this resolved?