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.
Find the customer's booking
Click on the booking to bring up the booking details screen
Click on the “Messages” tab
Under Automated Email > tick “Don’t send follow-up email”
Make sure to SAVE the booking
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.