you put the number plate as an auction starting at 99c

You May have had a Buy-Now price on the listing, but that would be taken off once someone made a bid.

On eBay auctions sellers do not get final say through ‘approving’ or ‘accepting’ the final price.  The final price is the highest registered bid i.e. there are no reserves on eBay auctions for number plates.

DO NOT LIST ANY MORE ITEMS until you read up on how eBay auctions work.