I am creating a booking system for a beauty salon and they have two separate rooms with two separate therapists, 1 for waxing treatments and the other for face treatments. They both have their own time slots and availability. A user would need to book them individually but also not be allowed to book a time if it overlaps the other treatment. The design I have come up with shows the separate times however I am having trouble making it simple for a user to understand that they can’t book treatments that overlap each other. In the example attached if they pick 3pm for a body treatment, I have greyed out the face treatments as those times are unavailable if 3pm is selected. However they could still book a face treatment at 3pm and a body treatment later.