That's a great question!
StyleSeat offers a number of tools for professionals to manage their booking, calendars, and more, but especially how their clients pay. Each professional has the option, and ultimately the responsibility, to mark/checkout an appointment as having been paid "CASH", to ensure that their client is not charged when they shouldn't be. As a general rule of thumb, before leaving your professional's location, be sure to let them know to check you out as "CASH" from their schedule, if you're paying/have paid in cash. That will ensure that they navigate to their schedule, mark you as "CASH", and stop ExpressPay from charging your card!