With the exception of joining a class-action lawsuit, what sort of recourse would a consumer have in this situation? Consumer advocates say any effort should start with a letter to the company, and, if that doesn’t work (it didn’t here) to try lodging a dispute with the credit card issuer. But some Dollar customers tried that with little success: Dollar sent the credit card companies receipts with their signatures. A spokeswoman for Bank of America said it was bound by Visa and MasterCard regulations on disputed chargebacks, and, if the merchant has the customer signature accepting a charge, there’s not much more it can do.

As a result, this situation is likely to quickly devolve into a case of “he said, she said.” In a letter to Ms. McKinnon, Dollar explained that while its agents were capable of making mistakes, the company strongly suggested that clients review the contract carefully before signing to accept. And the records indicated that she initialed to accept the “loss damage waiver” charge.

But even here, there’s the issue of potentially confusing language. Rental customers might say out loud that they want to decline insurance coverage, but then they may see something on the electronic screen that asks them if they agree to the loss damage “waiver.” You can’t blame a tired or inexperienced traveler for thinking that by clicking to accept the “waiver” they are waiving insurance, when, in fact, it means they are accepting that type of coverage.

Perhaps these consumers should have caught the errors on their receipts before they put the keys in the ignition, or they should have been more vigilant about what they were signing on the electronic tablet. The customers I spoke with all said they did as instructed, taking the agents at their word.

“We did not expect that, while the counter agent was smiling and verbally assuring us that we would not be charged for options that we had affirmatively declined and did not want, he simultaneously and apparently was including those very charges,” Mr. Seibert said.

In fact, if travelers believe they were intentionally misled, they can seek punitive damages through small claims court. Alexander Anolik, a travel lawyer and co-author of “Traveler’s Rights: Your Legal Guide to Fair Treatment and Full Value (Sphinx Publishing, 2003),” said to sue for misrepresentation, fraud or unfair business practices, all of which are torts and eligible for punitive damages. That may at least make the case worth your time and effort; Mr. Anolik said to ask for three times the amount you lost in damages.