When it comes to a customer not showing for a booking or cancelling a booking, the only way to do this is to tender payment (obviously with zero sale/cost). This then shows the booking as completed on the scheduler, implying that a service/sale was made. It would be better to be able to cancel the booking, however, to mark it as cancelled or as a no show, in order to highlight them. This could be done using a different colour and not including the $ symbol showing a completed sale.