What do you mean by "having withdrawn"?

If cancelled your NS Flex subscription entirely you should have received an email stating you need to remove this product from your card at a vending machine to finish cancellation.

If you changed an NS Flex subscription to NS Flex Basic - and were able to do so after having your subscription for at least a month - this change is effective immediately. If you did this close to the date of your next invoice, it is possible this was already created an was therefor still deducted from your account. In this case, this will soon be corrected through a new invoice. I assume the procedure is the same if you cancelled your subscription directly after ordering it without having used it.

If you're wondering why you still have to pay for each journey even though the money for a newly bought Traject Vrij season ticket has been withdrawn from your bank account: if you purchase an NS Flex season ticket for an existing OV-chipcard, and you did not have NS Flex on the card before, you need to load it onto the card at a ticket machine by picking up this order. You should have received an email about this. It sounds like you didn't do this yet.

You could contact customer service to get the money back you had to pay for jour journeys while the season ticket was already active, but not loaded onto the card. This can be done by phone; they are available 24/7 at 030-751 51 55. You may also contact them by chat (click the link Chat with NS on this page) or by sending a message on X (formerly Twitter) or Facebook.

I suppose @Loresichi means the subscription cost was withdrawn from his/her bank account, as well as the travel costs from his/her chipcard credit.

When subscribing for NS Flex for the first time, you'll need to pick up the Flex product at a ticket machine first. Only after loading this product on the card, the system will know you're using Flex and compare your travels with the validity of the subscription. Resulting in no charges when travelling from Zaandam to Amsterdam Centraal.