Tell the shop that you think that they made have made 'a mistake' (tech speak for 'trying it on'). I had a similar problem with some RAM a while ago. When the PC booted up it told me the RAM was half the amount I had paid for. "Oops!" they said and swapped it foe the right strip.
Back to the point, do you have anything in writing?
Unless you are seriously into audio work then a basic card will be more than enough. Get your money back, buy a card yourself (from somewhere else)and fit it <it will take longer to take the case off the PC than it will to fit the card>.
This one is well over the top and is only £10 click here