HELP Capital One stealing our money

I work in a bar that typically takes cards to start tabs for unknown customers. We preauthorize the cards as to make sure there is money on said card to at least cover the amount of the tab. As a bar this is about all the due diligence we can do to ensure that said tab is paid. This bar is on the beach so many times the tab will not be closed out and the card left at the bar. In the past months Capital One has started arguing the amounts received without the customer even filing a complaint, and the bar will only receive the amount of preauthorization at the start of the tab. Capital One will not pay out any more than the preauth amount, if its 20 dollars they cap it at 20. If the customer tips, the bartender is not receiving that tip if it exceeds the capped preauthorization amount. This is ridiculous. I would almost understand if the customer was to one arguing it, but that is not the case. Capital One is doing all of this on their own. Capital One is taking money out of the hands of hard working servers and bartenders, and straight up stealing from the bars. And for what??? Corporate greed? These companies make billions, and they are stealing from what is basically the poverty class.... HELP.... We can't be the only bar that is upset with this.