Q: We rented a car from Hertz in Cancun, Mexico, last spring. We paid for the highest level of insurance coverage offered, which was described by the Hertz agent as the insurance that covered any damage that might occur to the vehicle during our rental.

While driving on the highway called the Riviera Maya the oil pressure warning indicator came on and we drove to the shoulder of the highway. While we were pulling off, the engine began knocking and stopped. In my examination of the car, I found that oil filter was damaged and oil had leaked out of the engine causing the failure.

We called Hertz and they quickly responded by supplying a replacement vehicle. At the end of our rental period, we were invoiced the agreed rate for vehicle rental. The ticket agent mentioned that I had just experienced the reason to take out vehicle damage insurance from Hertz and that there were no charges related to the problems with the first vehicle.

At our next Visa card billing we found that Hertz had billed $2,989.51 to our credit card in charges dated a week after we had returned the vehicle. These fees were additional to the costs of renting the car. We received no description for the reason for the large added charge.

We called Hertz beginning in May, writing letters and making calls, and the only response we have received said that no refund would be authorized. We did receive information that the charge was for an engine replacement but there was no explanation for why our insurance didn’t cover this vehicle damage. With further protest, we received a letter on June 21 that said the Cancun office has been requested to review the charges. We’ve heard nothing further.

We don’t believe Hertz has honored the coverage offered in their insurance. And the resolution process does not seem to be moving toward conclusion. We request that Hertz refund the fees charged for engine repair. Can you help us?

– Frederick Gunkel

A: Yours is an all-too-common story. You rent a car, put a dent in it, are told it’s covered – and then during your next billing cycle, discover mysterious charge that turns out to be a bill for the body shop.

What sets your case apart is that you were reassured by several people along the way that this would be covered under your insurance.

According to Hertz, it wasn’t.

True, you bought the deductible damage waiver, which takes care of accidents, total loss or theft. But the company says this was no accident.

Hertz’ records suggest that the oil pan and filter in your vehicle were damaged following an impact with the undercarriage, such as hitting a large pothole or speed bump. The repairs for that would have been covered by your insurance. (I should note that in the part of Mexico you were visiting, extra-large potholes and log-sized speed-bumps – sometimes referred to as “sleeping policemen” – are everywhere.)

However, Hertz contends that you continued to drive the car after the collision. The engine lost all of its oil and broke down, at which time it claims you called the roadside assistance number.

I’m troubled by the way your entire grievance was handled by Hertz. Why would you reassure a customer that certain damage is covered by insurance before you’ve had time to even examine the car? And simply billing a client’s credit card without so much as an explanation is dreadful, substandard customer service.

Hertz shouldn’t have told you not to worry about the damage. It should have notified you promptly, in writing, when it discovered the extend of the problem and it should have been far more responsive to your questions regarding the incident.

Next time you rent a car, remember to be extra careful. Treat it as if it’s your own set of wheels. If you think you might have damaged the vehicle, don’t wait for an engine light to come on – pull over at a service station and check it out.

“Unfortunately, due to his negligence in not contacting Hertz immediately upon impact to the underside of the car Mr. Gunkel did violate the terms and conditions of the rental agreement,” said Paula Stifter, a Hertz spokeswoman. “Accordingly, he was charged for the damage and no adjustment to Mr. Gunkel’s bill is warranted.

My hands are tied on this one. I would check with your car insurance to see if some of the damage can be covered, but there’s nothing that can be done about your bill. I’m sorry.