Beste antwoord door Loes
My English talking is better then writing. I will try to explain it to you.
If you want to travel with discount, our rules are that you have railcard with a abonnement (subscripton) on it or you are travelling with someone that have a abonnement. Than it is allowed to travel with a ticket with discount. Well, what I'm reading is that you didn't know this rules and the conductor wrote you a fine.
She did her job, so if someone does not have a valid ticket, we'll write a new ticket with the fine (that's in Dutch law). However you can call customer service to tell them you didn't know this and ask of they will cancel the fine.
On you're new ticket, also you're fine is a number in the top on the right and will begin with a D followed with six numbers, for example D123456. This number the customer services will find you're fine and then they can tell you what is to do with the fine, so if it's cancelled or not. Hopefully they will cancel it, but I don't know.
The NS customer services you can reach on number:
Monday till Friday from 08:00 to 22:00 our and on Saturday from 09:00 to 17:00 uur on telephone number 0900 - 20 21 163 (€ 0,10 per minute).
If you have a foreign number, you can call on number 030-7515250 (+31307515250).
A student must also have a abonnement for travelling with discount and that is arranged by DUO.
I hope I helped you with some information. Good luck