Sellers don't usually open disputes when an item is not purchased. There is no transaction to dispute.
Do you mean the seller is claiming that you did not pay?
If so go to your Paypal account, find the payment and give that transaction number in the dispute.
Don't worry too much about the names. A seller can have different names on an account: personal (Jane Doe, Chou En-lai), eBay ID (e_drew, reallynicestamps), shop name (Jerry's Favourites, BestBeeHoney),Paypal ID (an email address).
But you believe there was a duplicate order, for which you did not pay?
And the seller cancelled that order?
Can you find the eBay transaction number of that purchase?
Your seller may be confusing the paid (and shipped?) order and the cancelled (unpaid and unshipped) order.
And also language difficulties. And China is just finishing up the Lunar New Year holiday when businesses are likely to be short-staffed.