Of course the seller should not be rude or make threats.
However, whatever Ebay say, surely you can see that you should not feel entitled to keep the item and your refund?
If you no longer want the item, ask the seller to provide a label for return.
If you want to keep it, ask them how you can pay them.
That way, this will be settled fairly for both parties.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)