It sounds like you had a Weekend Vrij subscription without the discount during off-peak hours on workdays and wanted to add that discount later, but instead changed your subscription so you now only have the discount during off-peak hours.

Since you cannot change your subscription again until a month has passed since this change, you should contact customer service directly to explain the situation and have them change the subscription for you. Usually, this is most easily done by phone, as they are available 24/7 at 030-751 51 55. You may also try to contact them by chat (click the link Chat with NS on this page) or by sending a message on Twitter or Facebook.