I received a reminder email that I haven't paid yet

If the amount has been debited from your account, you have indeed paid the order. The email was sent because you may have accidentally placed your order twice in a short time, this sometimes happens when you click back between the different steps during the ordering process. The solution is: click on the link 'Go to payment menu' in the reminder e-mail. Then click on 'back to webshop'. Now you won't get the reminder anymore.