If you can, return it as it sounds like you got cheated.
However, if you can't, all is not lost. Here's what to do:
1) Look at the memory chips on your card and write down what's printed on them.
2) Go to the samsung website and look up what kind of memory chips you have. If the chips you have are capable of running at 340 mHz, you're in good shape.
3) Download the 9800 Pro BIOS and flash it over your current BIOS. If your memory is good enough, your card will now be equivalent to a 9800 Pro.
*WARNING* -- you can render your card useless by doing this! Please make sure you look around on the net and read about what you're doing first. I suggest the forums at
www.overclockers.com for more info.