Thanks for reaching out to the Community! I am happy to help you turn off those invoice reminders! I see you mentioned your automatic email reminders are disabled, but we will want to make sure we have the invoice reminders disabled as well.
Go to Settings and select Account and Settings.
Select the Sales tab.
In the Reminders section, select Edit .
Turn on Auto invoice reminder.
Make sure to save your changes!
If this for any reason does not solve your issue, please reach back out and we can take a deeper dive. Take care!
I appreciate the things you've done to make sure that the recurring transaction is not turned on.
Since you've performed the troubleshooting steps given by my colleagues, I'd recommend contacting our QuickBooks Online Support Team. They have the tools to verify your account, then check for any possible reasons why you're experiencing this.
Navigate to ? Help and click Talk to human.
Enter your concern such as "Invoices has been sent out to my customer without the recurring transaction turned on."
Select the I still need a human button.
Click Contact Us.
Choose how you want to get assisted either by messaging or getting a callback.
Enter your details on the pop-up window and confirm your request.
I've added this reference page in case you have other questions regarding QuickBooks Online: Help Articles.
Please don't hesitate to comment below if you have other questions. I'd be happy to assist you further. Take care.