If they open a return case through Ebay and they claim the item is not as described in the listing, you will have to choose one of the options offered by Ebay.
Essentially, you will be expected to refund without return or supply a return label and refund when you get the item back.
Until/unless the buyer starts a return case, you don't need to do anything.
"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)