If a customer complains after their visit and you don't want Collins to then send them the automatic follow up email, you can disable it from the customer's booking.
In your main booking enquiries list, search for the customer.
Click on the booking to bring up the booking details screen.
Click on the “Messages” section
Tick “Don’t send follow-up email”. Note, this will only be visible if you've turned the automatic follow-up email on in your settings. Follow this guide to learn how to do this.