Hello,
It had happened to me aswell. It is fairly simple to resolve by complaining to E-Bay. E-bay just remove the listing, if there are more listing they strip off user ID aswell.
One guy copied pictures of my "Nice" Bras and removed only the edges where e-bay logo displayed.
First i thought it is my listing and picture misses something. Finally i understand he is copied everything from me.
You go to e-bay help, then select report a selling problem, then report problem with other seller, select "Listing copied " You have to give comparison like your Item ID and similar listing number from his Item ID. With in 24-48 hours, other guys's listing will not be there. But make sure your listing is created before he created by verifying he serial number of the item id. Like this you report around 4-5 items in different category.
E-Bay definitely helps hard working genune sellers like us.
Goodluck.
Regards,
CoolBrasCo