Solution

1. Go to Administration >> Service Charges
2. Click on to edit the Service Charges
3. Click on Service Charge Details, ensure the Service Charge has the column Debtor set to All Debtors. (You can restrict by debtor in the next step).

4. Click on Visibility and Ledgers tab >> Select the Available for
   

4. Select the Debtor(s) the Service Charge is to be made available for.
5. Click on Save.
   
6. When booking an Appointment using that Service Charge, the Charge To can only be changed to the Debtor(s) in the above Selected Debtors table.