Quickbooks just sent payment reminders to my customers without my permission or knowledge!! what!

I'm glad to have you here, @amy190.

Let me share info on why payment reminders were suddenly sent to your customers without you doing it and help you fix it.

You might have turned on one of the Reminders in Automatic Invoice Reminders. We'll need to turn it off. Here's how:

1. Go to Settings ⚙ and select Account and settings.
2. Select the Sales tab.
3. In the Reminders section, select Edit ✎.
4. Select the dropdown for Reminder 1, and turn off the toggle switch.
5. You can also turn off the Automatic invoice reminders as general.

For more info about this, you can read this article: Send invoice reminders automatically or manually in QuickBooks Online.

Moreover, you can check the audit log to when the automatic reminder was turned on and how it was done. 

if you want to personalize and add specific info to your sales forms, check out this article: Customize invoices, estimates, and sales receipts in QuickBooks Online.

For additional questions about payment reminders, click the Reply button below. I'll be willing to help. Have a good day.