If you want to disable phone call reminders (or SMS, Email) then go to Calendar> Edit Calendar > Edit on the calendar you want to edit. There are 3 switches at the top. You can turn off SMS, Email or Phone calls. Click save down the bottom. You will need to repeat this for all the calendars you have added to Appointment Reminder.
The settings in each calendar override the settings on each individual appointment. So even if an appointment is marked to send email but email is turned off in calendar settings then an email reminder will not send.
