What should we do regarding an unathorized credit transaction due to accidental damage at a restaurant?

My son accidentally cracked a restaurant table's gl cover. We left our name and cell number to the waitress since the owner was not there at that time. When we checked our credit card statement, there was an extra $99 billed from that restaurant. Is this even legal? We did not authorize this. Don't they have insurance to cover such incidents? Why did they not call us before doing anything so we have the option of asking them why it costs $99, why their insurance does not cover such damage. I believe it is illegal to charge something without authorization, right?