If you rent a car from Hertz in San Francisco, it’ll automatically pay the toll for crossing the Golden Gate Bridge. But the city says in a new lawsuit that the rental car company is gouging tourists by fraudulently charging them millions of dollars in extra fees.

City Attorney Dennis Herrera filed the lawsuit [PDF] in San Francisco Superior Court on Wednesday, accusing Hertz and its toll-processing partner American Traffic Solutions of misleading customers and engaging in unlawful, unfair and fraudulent business practices with its toll service.

Hertz offers customers an automatic toll-paying service called PlatePass that they can use on California’s toll bridges, or just pay cash. Since the Golden Gate bridge went totally cashless four years ago, motorists can use a FasTrak toll tag, or pay online, in person, or by phone after their car has gone through.

The lawsuit claims that Hertz doesn’t tell customers about these other options and instead, once they drive over the bridge, PlatePass is triggered. Hertz customers are charged an undiscounted toll rate of $7.50, the city says, as well as a $4.95 “convenience fee.”

But they often aren’t charged that fee once, according to the complaint, and instead can be hit repeatedly by that fee for up to $24.75. That’s a pretty pricy bridge crossing.

Although Hertz calls PlatePass an “optional” service, the lawsuit claims that for many customers, “the first and only time” they are provided any information about PlatePass during the rental process is on the fourth page of a six-page rental record, under “Important Information Regarding Tolls,” which reads:

“IF YOU DO NOT WISH TO USE PLATEPASS IN THESE AREAS, use only traditional cash toll lanes (if available) and make payment directly to the toll authority.”

That page doesn’t mention the Golden Gate Bridge specifically, either, or inform customers of the other ways to pay the toll.

Not only that, the city says Hertz and PlatePass make additional false and/or misleading statements with respect to avoiding or opting out of the service on the Golden Gate Bridge.

For example, the Hertz website says, “If you don’t want to use PlatePass, you must pay all tolls with cash (if the option is available) or with your own toll transponder compatible to the toll road.”

The PlatePass site also indicates that the Golden Gate Bridge is among those facilities that no longer accept cash: “If you use any of these facilities without using a personal toll transponder you will be charged for using PlatePass as no cash option is available.”

Making matters worse, San Francisco says, Hertz doesn’t charge and disclose the fees itself on the receipt it gives customers when they close the rental, but instead provides its customers’ confidential personal credit card information to a third party who slips in the charge at a later date.

“Hertz customers who crossed the Golden Gate Bridge never accepted nor chose the optional PlatePass service nor did they receive its benefits,” the lawsuit says. “In other words, they never ‘used’ or ‘utilized’ the service, thus defendants should not charge them for it.”

The toll charge is also improper, the city claims, because the defendants have charged customer $1 more for Golden Gate Bridge tolls than what the defendants paid.

“These practices are not only unfair, they’re unlawful,” Herrera said in a statement. “Rather than Hertz putting you in the driver’s seat, they’re taking their customers to the cleaners. I am not going sit back and allow one of the largest rental car companies on the planet to take advantage of a world-renowned San Francisco icon to rip off thousands of California visitors and residents.”

The lawsuit alleges that the Hertz Corporation and American Traffic Solutions, Inc., engage in false advertising and unfair, unlawful and fraudulent business practices in violation of several state and federal consumer protection laws, including California’s landmark 1988 legislation that specifically prohibits abusive practices in the rental car industry. It’s seeking a court order halting the allegedly deceptive practices, restitution (with interest) to victims, and civil penalties of up to $2,500 against each defendant for each unlawful act.

Hertz isn’t the only car company engaging in allegedly shady tolling practices, Herrera’s office said, but the city singled Hertz out because it makes it so difficult for customer not to use PlatePass. He didn’t rule out going after other car rental companies.

“Based on our investigation, Hertz’s practices were the most egregious in terms of both misinformation and gouging customers,” Herrera told SFGate.com. “Hopefully this lawsuit sends a clear message that other companies heed.”

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