You're probably using NS Flex. With NS Flex all your travelling costs (train, bus, metro, tram) will be charged monthly to your bankaccount. The balance on your card is not used with NS Flex.

For the train this is the new system and it will be-or at least that is the intention-how the system will work for all transit in future. You did not clearly tell if you also hold a subscription for discount or whatever for trains/NS.

IF you do not like it, you can call NS to suspend this for bustram, but never for trains. IF you also want that, buy a new blue chipcard-on which you cannot load any subscriptions. The current balance (saldo in dutch) can be paid out at any staffed station-MAX 30 eur, for more via ov-chipcard