even though in the account settings/sales Invoice payments are set to off, they are still appearing when an invoice is created

Any changes to the Invoice Payments settings will only impact future invoices and will not retroactively affect previously created ones, Andy.

If you prefer that the Customer Payment option section doesn't appear on an existing invoice you created, you can manually turn off the feature.

You can manually toggle off the Payment options section to prevent the Customer payment from appearing on the invoice. I've added a screenshot for your visual guide: 

To give you more information about the Advanced account settings, where you and your accountant can set up your company file initially, check out this article: Set Up Advanced Account Settings in QuickBooks Online.

Additionally, learn how to receive and record invoice payments once you turn off QuickBooks Payments. I've got this resource for more details: Record Invoice Payments.

Did you know that our QuickBooks Live Expert Assisted team helps you optimize your business and is available on demand to help you make the most of your transactions. They will help you to have a clear understanding of your business performance.

If there's anything else that you need about your customer's payment or anything on your invoice settings, let me know by posting a comment below. I'm always here to assist you further.