Co-owners of Bru Cafe David and Jacinda Reid opened their cafe, in Moray Pl, in February.
They began opening on weekends, and soon after were making enough money on Sundays to rival that of Monday.
At the end of September, Mrs Reid received an unexpected phone call from a man who introduced himself as an "automated service through Google phone services for business hours".
After inquiring about the cafe’s business hours over a series of calls, Mrs Reid specifically told him their hours were the same as those already listed and did not need to be changed as she and her husband updated the hours themselves.
She did not think anything would come of the phone call, but over the next five weeks their Sunday revenue plummeted from nearly $450 to $75.
According to her Google account, the hours listed online had been "updated by phone call" exactly five weeks prior, to say they were open on Saturday but closed on Sunday.
Mrs Reid said the phone call coincided with the drop in business.
"Our efforts to get better were spoilt by someone doing something as careless as updating our hours incorrectly.
"Whether he is employed by Google or whether he is just a guy who feels he is doing a public service, I’m not sure."
After correcting the information herself, on the next two Sundays the cafe doubled its revenue and within two weeks was back to normal.
She had racked her brain to find other explanations for their drop in revenue, but could not find another feasible cause.
She said the man was unhelpful and "didn’t want to have a bar of it" before abruptly hanging up.
She had reason to believe the man was contacting other Dunedin businesses, as she recognised him from previously working as a manager at Heritage Coffee, in Vogel St, Mrs Reid said.
She called the situation "heartbreaking" and demanded accountability.
"It’s distressing to know that someone can just update your business hours without your consent ... It can have such a huge impact and actually they don’t have anything to do with our business at all."
A Google spokeswoman said they were still investigating the issue but it appeared to have been outreach from its automated calling system.
Google used a variety of sources to get the most accurate and up-to-date information on the map and a combination of manual and automated techniques to check for accuracy.
"When there’s an issue, we work to fix it as quickly as we can," the spokeswoman said.