Summary
Globally manage Appointment Reminders from Settings/Appointment Reminders. Override the global Appointment Reminders for each individual account from within the customer's Location page.
Key Points
Edit a customer's Location page
Update the preference at the bottom of the page
Go into a customer's location page and click the Edit button at the top center of the page. At the bottom of the Location page you'll see Send reminders...
If you have this setting set to as per account settings, Fieldwork will use the configuration you have set up Settings/Appointment Reminders to send a reminder to this customer.
As per account settings means your Fieldwork account, not your customer's account.
If a customer does not want reminders and you have Settings/Appointment Reminders activated, click Inactive.