If they haven't taken down the false and libellous review, you can flag it for Google to respond to the situation. Follow this procedure for flagging the fake review. Looking to delete a Google review? You can respond to the reviewer and suggest removing it if you are able to take the conversation private. If that doesn't work, you can flag the review for Google, or get in touch with their support for small businesses. You could also expedite the process via Twitter. One of these options should help you remove malicious or fake reviews from Google.
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