There is a possibility for multiple or return calls. Sometimes, an existing appointment can be used if the service is still related. However, if not, there would be a new service created.So another example of a future feature that will be needed. Eventually your call list will get extremely large with old calls. That list will no longer be useable.
I can envision an option group at the top of the list to filter what you want to see.
Calls needing appointments
Calls with appointments
Open Callls (both of the above)
Closed Calls (ones with a service "call details")
The default is probably "open calls"
Also I did not add a place to put "Call Details", which if I understand is basically a record of service. When it started and when it completed. Also that table may need to get rethought. Currently a call comes in requesting service at a specific property. Then you schedule an appointment. You can schedule one or more appointments against that call. Which makes sense if the problem is not resolved. But if call details is the actual start and end times of the service (you would also need a actual date), the relationship is such that you could have multiple services against the same appointment. If that is not really the case and an appointment one service then those fields would go in the appointment table.
Apointmentdate
appointmentTime
ServiceDate
ServiceStartTime
ServiceEndTime.
If you make CallDetails a child table of an appointment but will never have more than one calldetail per appointment then that will create unneeded complexity. Instead of a couple more fields it is a whole new subform.