Unable to cancel order as a buyer

[tomsk3000]

I bid on an auction listing. I then realised the item was not an original but a modern reproduction (listed in the wrong category).  As the auction had less than 10 hours to run I was unable to retract my bid.  I therefore contacted the seller and explained the situation.  The seller was happy to remove the bid but was unclear of the process.

Later when I checked my ebay, I noticed that there was a request to complete payemt for the item?  I am unable to cancel this order and the seller does not know what to do.

I do not blame the seller, as I appreciate how complicated ebay can be, especially for fairly new sellers.  I would just like to know how is it possible for a bid on an auction listing to be converted into a 'buy it now' bid without the buyers consent?  Surely the software should have inbuilt protection against this happening?

[tha-3817]

I purchased a laptop from eBay on the 25th of September and I'm not able to cancel the order.