Woo Sell Services has a setting area where you can customize all of the emails that are sent by your store.
Navigate to WB Plugins > Woo Sell Services > Emails, and check the emails.
These email templates can be overridden under your child’s theme.
The path will be like this:
Actual path: woo-sell-services/woocommerce/templates/emails/email-file.php
Override path: your-theme/woocommerce/emails/email-file.php