Hi koos.marietjie, thanks for sharing your query here.
I believe that you might be asking about the display of the invoice instead of the statement as the statement in QBO doesn't display any banking details.
Here's how you can edit the footer or message to customers in your invoice..
1.) Click on the gear icon at the top right
2.) Select Custom Form Styles
3.) Click on Content and then click on the bottom portion of the preview on the right
4.) Here's where you can make the text entry such as your banking details for your customer.
Be sure to click on Done after you've make the changes to save them
I would like to confirm that "IntuitKaiXiang" is correct - the way to change the footer of the customer statement is by changing the invoice template. There is no place to edit a template specifically for the customer statement, rather the customer statement will use the same template as your invoices. I have multiple invoice template styles, but it appears that my customer statement was using whichever template is designated as the "Master" form type. This is shown on the custom form styles page (Gear Icon -> Custom Form Styles). By editing the Master template you can update the information shown on your customer statements.