I can guide you on how to stop the recurring sales invoice you've created, Nicola.
You can either delete the recurring transaction or edit the template to Unscheduled or Reminder type in QuickBooks Online (QBO).
I have articles here about managing your recurring template in QBO:
I'm confident the steps provided can help you stop the recurring sales invoice to generate in your account.
Just reply to this post if you need anything else with recurring transactions. I'd be glad to help.