You can learn how to stop automatic invoice sending feature just for specific customers.
1. Open Easy Invoice+ from Apps section of your Shopify store or go directly to https://easyinvoice.softify.co/
2. Click “Customers” from left menu.
3. Click on the mini green paper icon from “Actions” column to view and edit your customer details.
4. If you uncheck “Automatic invoice delivery” you can prevent sending invoices automatically just for this customer.