I offered 7 of something on EBAY, someone used "buy it now" to buy 3 of them but somehow did it twice. There seems to be no way to cancel that duplicate order, well from a seller point of view anyway, must the buyer cancel this? Any ideas anyone?
You would have to open a dispute on eBay, and ask the buyer to cancel 3 of the transactions. This is quite easy to do - I sold something recently but needed to cancel the sale before sending to the buyer, the buyer gets an email from eBay asking them to confirm the sale is cancelled, as soon as they do that, you can relist the items (and you get final value credits for the items bought by mistake).