If you have a problem with your bill after 24 hours the desk cannot help you. You have to call Customer Relations/Billing. They are open 7 am to 7 pm (CST) Monday to Friday. 1-800-654-4173
Make sure the individual renting the car (driving) is also the person paying. They are ridiculous. Even if your spouse is paying. Then they want to charge extra to "add a driver"