I had the exact same thing happen and posted an almost exact same rant a few days ago 🙂

Ebay told me they will not remove the feedback.

Ive just had another return for item not as described, that states something that WAS described very clearly in the listing, so as soon as ebay **bleep**s that one up too, ill call them and wont let it down until they remove both of them.

Threaten them with the ACCC, as this is not a fair business policy. You made a legally fair sale, and Ebay does not have a legal right to force you to refund the buyer. Tell them that and threaten them with the ACCC if they try to.

Demand to speak to a supervisor (and keep demanding it and calling until they do), get names / times / dates of your phone calls and ask if they record phone calls - request that they do.