Hi...
You might have your "Buyer Requirements" set not right, double check it in your ebay summary page under "Account" then select "Site Preference".
By changing it will not change the live listing now you will need to start a new listing with the number of items and the agreed selling and shipping cost, if you do decide to make the new listing, in the title put the buyer ID in it and tell them to do a search on their ID and they will be able to find it fast, it will also keep all the rest of ebay member from snatching from them.