Did you book a car though but didn't actually picki it up?
Pending charges are not charges and , assuming you reserved a car, there is nothing untoward in a hold being taken. The hold will drop off after a few days ( up to about 10 days depending on the card company )
There is nothing much that the credit card company will do unless an actual invalid charge gets applied to the card; there is nothing fraudulent about taking a hold for a booking
If you didn't reserve a car at all, then if a real charge gets applied, call the card company