You can easily buy credit for your OV- chipcard in the Keolis webshop. You put your order on your OV-chipkaart at a pick-up device. You can do that whenever it suits you. Find a pick-up device in your neighborhood. Click here for an overview of the pickup locations.
Did you know that you can also travel on balance with your debit card or credit card on public transport? For more information, go to:checking in and out with your bank card.