You are trying to sell a high risk item. By high risk, I mean high risk of being scammed. Before you do anything else, open up an unpaid item dispute 4 days after the first transaction ended. So, Monday afternoon at 2.52pm, go to the dropdown next to the item in your selling page and select the option that refers to an unpaid item. Exactly 4 days later (to the second), you can go back to that dropdown and select close case. On the screen after that will be the transaction and a dropdown to the right of it. Select the option to get your fees back. On the next screen, if the option to select no isn't able to be clicked on, then the 4 days isn't up. The earliest time you can close will be at the top of that screen.
Exactly 4 days after the second sale ended, do the same. Closing the cases will get you your fees back. If you cancelled the transactions, then you can't open an unpaid dispute. If you did elect to cancel, you just have to hope the scammer doesn't hit decline on the request or you lose you fees.
Next, go to http://offer.ebay.com.au/ws/eBayISAPI.dll?BidderBlockLogin and add both the buyers to your blocked buyer list.
Then go to http://offer.ebay.com.au/ws/eBayISAPI.dll?BuyerBlockPreferences and set up blocks. They are not fool proof, but can weed out majority of scammers.
Buyers with unpaid strikes, select 2 in 12 months
Buyers in a location I don't post, tick
Buyers with policy violations, select 4 in 6 months
Buyers who haven't gone through phone verification, tick (most scammers haven't phone verified their account).
Apply above settings to current and future listings, tick
Don't allow blocked buyers to contact me, tick
Submit.
The buyers who've bought from you are scammers. They will probably ask you for your PayPal email address so they can pay. Don't give it to them. Don't give them any details at all. They will then try and get you to post it to their cousin in Nigeria (or another scamming country). Don't reply to any emails they send. Cut all communication. Report them to eBay via the help and contact page at the top of any eBay screen.
If you have given them your PayPal email address, be careful of phishing emails from PayPal that look authentic. Never click on any links in emails, especially from PayPal. Anything in an email can be checked by logging into your PayPal account via a browser.
Edit: If you did cancel the transactions using the cancel option, you need to go back in 8-10 days and close it to get your fees back. Don't let them time out because I think you lose your fees if you do. You stand to lose a fair bit, so make sure you get it right!
