As a seller, selling quite a lot of Brand new items, you should know the answer.
Buyer opens a not as described case, you provide a return label and on return refund in full.
Selling new items means you should be registered correctly, and have a proper return policy giving buyers their legal rights.
Any buyer buying new should be entitled to return for any reason for a refund, by ebays rules for change of mind returns, buyer pay the return postage, for not as described seller pays.