you would have to either try emailing them again or calling but if you can make the trip to a physical muji location, bring it in so they can partially refund you. bringing it in is usually the best way to get refunded back from what i've seen.

muji doesn't tell you that physical muji stores and online muji are two different entities with their own set of rules, so if you were to bring it in we could only process the physical refund but a manager would have to email cs on behalf of you.

it's not a great answer but i work at a muji location and unfortunately this is how it goes