You need to report this to eBay ASAP. They will probably want forwards of the emails as proof, so the more of them you still have the better... but even if you don't have any you should still report it so the complaint is on record. (If a Seller with that kind of volume is doing that to you, chances are they are doing it to other people as well, so it is important that it gets reported so eBay can see their pattern of behavior and eventually take action against them. If no one says anything to them, the Seller appears to have done nothing wrong.)