How can I change my bank account number from which the invoice is debited?

Go to Company settings > Payment methods. Here you can find an overview of your current payment method(s).

Here, you can also add a (extra) payment method by clicking on '+Add payment method'. When you click on '+Add payment method' you will see this screen where you add your (new) bank account number:

If this new payment method replaces the other payment method, you can delete the 'old' one by going to 'Payment methods' and then clicking 'View'. On the top right, under the cog icon, you can then choose 'Delete payment method'. You can also choose to leave it in place, but make it inactive. This is done automatically when you activate another payment method.