It read: "Very efficient - in three days my laptop has been repaired. I have searched for the least expensive repair for my Macbook Air until I found this repair shop."
The 19-year-old sent a text to the owner of CER Computers, who told her they had been hacked.
"I said, 'But if that was true, why was my name and my account being used?' I felt like they'd violated my privacy, because I trusted them to fix my laptop, not to snoop."
Consumer NZ spokeswoman Jessica Wilson said if a company was accessing customers' emails to write fake reviews, it risked breaching the Fair Trading Act and Privacy Act, as well as the Crimes Act.
"The Fair Trading Act prevents traders from making false or misleading representations. This includes posting fake reviews."
Wilson said companies risked being fined up to $600,000 for breaching the act.