Your subscription is continuous, which means it will not end until you explicitly end it.

For this, you should contact customer service directly. This can be done by phone; 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.

Be sure to explicitly mention that you are abroad. Usually, to end a subscription the subscription has to be removed from the card at a ticked machine. As you are abroad, that can’t be done. Customer service will end the subscription in a different way then, which in turn leads to you not being able to use that card for another subscription in the future.

Why didn't you terminate it before you left?

Some possible reasons:

1. When moving, especially when moving abroad, you have lots of other things on your mind.
2. You can usually cancel subscriptions shortly before they're up for renewal, so you don’t need to do that immediately when moving. Of course, you should then remember to do that later.

and 3: one still needs that card for the final trip out of the country-to airport or busstation.

Plus that its a bit different from what most other countries want from the client to do in such cases.

However, when one terminates forever the stay here, in most cases the bank account is also terminated.

@HaO: you will probably now get extremely difficult problems with either that bank or an encashment procedure due to missed payment.