Here are a few things you can do:
- reply to the fake or bad review - something along the lines of "Sorry you've had an unsatisfactory experience, but we don't seem to have you on record as one of our customers or having made an enquiry. Perhaps you have mistaken us for another business? If not, please get in touch with us at customersatisfaction@xyz.com.au so that we can fix things up for you". That way, viewers will no only doubt the review, but also see your attitude and approach towards customer satisfaction.
- you can also "flag as inappropriate" if you are confident this is not a legitimate review:
- you can also ask Google to take down the review if you can provide evidence that it is fake or spam (you can submit this through your Google My Business portal). In this particular case, it looks like he left a bunch of 1-2 star reviews at around the same time, with no comments - maybe he didn't know what he was doing as he had just joined as a Google Local Guide (you should also point out that you have no records of this person being a customer or ever making an enquiry).
- consider putting together a mini campaign to get your customers or trade partners (e.g. suppliers) to do a Google Review for you. We can create an easy one click link for you to simplify the process, and pretty soon the good ones will overwhelm the one bad ranking.
Hope this helps!