Appointments-How can I book Service "A" during morning hours and Service "B" during the afternoon?

[Asellers01]

That's the general setup I'm going for.  The details are, I am photographing Christmas Mini Sessions on one day for about 6 hours.   The first 3 hours are without a Santa.  The 2nd half is with a Santa.  Pricing is different depending on which service is booked.

First time working with appointments.  When I set the schedule, it appears customers can book either service for either time block, and this is not what I'm going for.  

Need help working around this scenario.  Any tips or suggestions you can provide?  

Thanks.