In the old appointment screen when is guest is banned, it would pop up a warning box and ask if you would like to continue. Then new appointment screen should do the same thing, inexperienced staff may not see the box that says someone is banned and it does not try and stop you from booking the appointment. It could also be solved with the same type of box that pops up when you try to book a service provider with a service they are not trained in. It needs something more to stop people from booking banned clients.