just FYI, If you're in the states, and they send you a product you didn't pay for, you're legally entitled to keep it. whether that sits ok with you ethically is another thing entirely, but you're legally fine.
I'm trying to look up the law right now, I'll get back when I've got it.
http://consumerist.com/2009/02/dsws-dirty-trick-backfires-now-customer-has-free-shoes.html
Here it is, the FTC's unordered merchandise rule:
Unordered Merchandise
Whether or not the Rule is involved, in any approval or other sale you must obtain the customer's prior express agreement to receive the merchandise. Otherwise the merchandise may be treated as unordered merchandise. It is unlawful to:
1. Send any merchandise by any means without the express request of the recipient (unless the merchandise is clearly identified as a gift, free sample, or the like); or,
2. Try to obtain payment for or the return of the unordered merchandise.
Merchants who ship unordered merchandise with knowledge that it is unlawful to do so can be subject to civil penalties of up to $11,000 per violation. Moreover, customers who receive unordered merchandise are legally entitled to treat the merchandise as a gift. Using the U.S. mails to ship unordered merchandise also violates the Postal laws.
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Cancelling your order was revocation of your request to be sent the mercahandise.
So you should be pretty much good to go.
If you want to play it safe and do the right thing, send it back, but I'm pretty sure you're covered legally.
That said, I'm no lawyer, so you may want to check with someone who is.
-m