A Dollar rent-a-car return sign is seen on a lot near the Detroit Metropolitan airport in Romulus, Mich. (Rebecca Cook/Reuters)

If you rent a car while traveling in a state with electronic tolls, and you don’t have your own transponder, you could end up paying a lot more.

One Florida couple found that out the hard way when they went to Dallas for a funeral. Stephen and Anne Sallee say they were charged “false and inflated ‘administrative fees'” in a lawsuit filed against Dollar Rent A Car. In 2013, they went through four toll booths on the North Texas Highway that cost $4.70. They later received a bill from Dollar Rent A Car charging them an additional $15 per toll in “administrative fees” for a grand total of $64.70, the suit states.

“Dollar has misrepresented additional rental costs as “administrative fees,” which has misled and caused damage to consumers,” the class-action lawsuit filed in a Tulsa, Okla., U.S. District Court in May states.

Lark-Marie Anton, a spokeswoman for Hertz, which owns Dollar, said the company does not comment on pending litigation.

According to a 2007 study cited in the lawsuit, electronic tolls improve traffic flow, fuel economy, and reduce congestion and accidents. They were first introduced in New York in 1993 with E-ZPass. Today, 15 states are in the E-ZPass network and use the same transponders. Other states with electronic tolls use their own transponders, according to information from U.S. General Services Administration and EZ-Pass.

States with electronic tolls

Drivers who rent cars within the state or states that use the same transponder can use their own, but if they’re elsewhere, these are the extra charges they’ll pay.

How much rental car companies charge per day to rent a transponder

Per day transponder fees for Dollar and Thrifty vary by state. In Florida, for example, it can cost $8.99, while in California, it can be $10.95.

In addition, rental companies may also charge extra fees for every toll, as the Sallee’s allege in their lawsuit. Enterprise, which owns Alamo and National, charges $14.75 for every toll. Dollar and Thrifty charge $15 per toll if a customer does not elect to opt into using PlatePass. Hertz and Avis do not.

Last year, Hertz settled a $11 million class-action lawsuit over customers who said they didn’t know they’d be charged for renting transponders even if they didn’t use them, according to Bloomberg Businessweek.