If the customer actually wants the reservation that they are paying an automated service to secure, then neither of these proposed solutions will have any effect.

If the people running this scheme are profiting from it, soon they'd start using stolen CCs.

CCs aren't stolen that often (usually it is the numbers that are stolen) so it would be pretty difficult to actually pick up the reservation, assuming the restaurant is smart enough to demand that the CC be shown when the diner show up.

Temp CCs. There may or may not be money on it when the fee comes in..

Sorry, meant to say: charge $3 for a reservation, not a $3 cancellation fee. Deduct that cost from your bill for the meal.

Require the CC to be shown to the waiter when you come for your reservation - it is not that hard.

Authorize at reservation...