Do you mean you're still travelling on balance? If you ordered the season ticket for an existing card and you did not have NS Flex on that card yet, then you need to load NS Flex onto your card at a ticket machine. The season ticket is not active until you do so. You should have received an email with instructions about this.

Do you mean you see “Reizen op Rekening Trein” every time you check in, implying that you're still paying for every journey? That's not the case. At the end of each month NS will only charge you for the costs that are not included in your season ticket, even though it always says “Reizen op Rekening Trein”, regardless of which season ticket is active.

Welcome to the NS Community!

After (first time) subscribing to NS Flex, you need to activate it on your card at a machine (station, supermarket, etc.) by chosing ‘pick up order’.

After that, you don’t have to go to a machine when changing anything, except when you want to unsubscribe from NS Flex altogether (remove from card).

For your costs, contact NS Customer Service or see https://www.ns.nl/en/customer-service/refunds/refunds-when-you-forget-your-season-ticket.html