In preparation for a July 2005 family reunion, Dr. Ah Yin Eng, a physician in Pembroke, Ontario, booked five rooms last August for six nights at a lodge in Yellowstone National Park, using, which takes reservations for lodging within many national parks.

Dr. Eng said he was prepared for the nearly $4,000 bill he'd face for the rooms. But what came next was pure clicker shock. In the confirmation e-mail message from Reservations-Services, the site listed an additional nonrefundable service fee of 12 percent, or $486, that had been charged to Dr. Eng's credit card.

"At first I thought it was a deposit, but when I saw they'd already charged me 12 percent I called and asked them why," Dr. Eng said. "They told me to get lost."

The charge, it turned out, was a fee levied by a handful of reservation companies with no formal relationship with national park lodges, but which, like any travel agent, can still take reservations on a lodge's behalf. Representatives of national park lodging companies argue that these reservation sites prey on consumers who don't realize they can book rooms on the Web sites of national park hotels free of charge.

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