Gave me a bad review for not undoing trade???

I made a trade ad, this person (idk girl or boy) DM's me and we do the trade. Like 10 mins later They text me again asking if we can undo the trade but like I don't see the text and I already traded the item by the time I did. And I told them I already traded it, then they told me that I left them on read and gave me a bad review???? Even though we already did the trade???