Welcome to the PayPal Community! I sincerely apologize for the inconvenience this has caused your business. The HTML code in your shopping cart buttons under the 'Postage' section determines the shipping costs added to a transaction. To offer free postage, you'd want to select 'Use specific amount' and enter 0.00 as the amount. I also recommend checking your settings through Wix as they have the option to add shipping costs to a payment as well.
