I have a "Voordeelurenkaart" ... and when I first used it, chose to travel on 1st class on the main railway lines.

Does anyone know if one can switch it to 2nd class? Rail ticket agents tried to do it for me at schiphol and said I have to go online to do it. But once there, the site says that I've already chosen .. and there isn't a click to change it.

Thanks.