If you have used an online travel reservation service to book a car rental (e.g. Priceline, Orbitz), pre-paid the reservation, and were charged extra fees and taxes, even though you didn’t agree to extra services, you may have a claim for breach of contract.
Many times an online service company will include fees and taxes as part of the reservation price. If these fees and taxes are actually charged to your credit card (versus just an estimate), the terms and conditions of the particular travel reservation service will govern whether you need to pay any fees and taxes at the reservation counter.
One travel reservation service in particular specifies that once the customer pays taxes and fees to the reservation service, any taxes and fees charged to the customer by the car rental company should be paid by the travel reservation service.