As long as you got refunded back for the second pay, then you should be well. The problem is the vendor has two E Bay sites for exactly the same item. You will need to contact E Bay over this. It seems like some sloppy E Bay postings. There are an increase in surplus stores in China advertised on E Bay. I have found some surplus stores in Singapore, Hong Kong, and South Korea. They all sell very quality and name brand items. This has not been a good year for E commerce. I bought a Mutoh drafting machine and it arrived broken. I did not returned it back, but repaired it myself. The pictured showed a perfect drafting machine, but the owner dropped it, before packing. I sold a Macintosh Portable on Craigslist and the buyer did not pay me for seven months during the great recession of 2008. I bought a pair of Street Skis and the bindings were defective and mounted in the wrong place, that I have to exchange the bindings myself and mounted them in the right place leaving holes in situ. The recessions have caused the sloppy on e commerce and manufacturing goods, too.
Please, complain to not just E Bay and Pay Pal, but to the seller via, "contact the seller," if possible. Be polite and clear that you were charged twice for the same item and asked why? Tell them that sloppy listing and charging twice for one item are not acceptable. I complained to the Street Ski maker, Macintosh Portable buyer, and Mutoh seller. I got them resolved on my own and eventually got paid after seven months!!! You are not alone with problems in e commerce. I want to buy two microscopes from main land China, when I have work, but I am hesitation over, if it went wrong, then who will help me?