Hello, please contact customer service at https://www.ns.nl/en/customer-service

The check-in at Amsterdam Sloterdijk at 17:59 was during peak hours, so full fare. You checked in and out again at Duivendrecht, but since the first check-in was during peak hours the entire journey is still full fare. Only if there is more than 35 minutes between the check-out and new check-in it will become two separate journey's and the second journey is against off-peak rate. 

For more info about this see https://www.ns.nl/en/travel-information/traveling-with-the-ov-chipkaart/frequently-asked-questions.html

The first check-in determines the rate. How does that work?

The first check-in determines the rate for your entire journey. Therefore, if you check in during off-peak hours, this rate continues to apply, even if you make a transfer during rush hour. Checking out and in during your journey to buy a sandwich does not affect the price of your journey. You must check in for the rest of your journey within 35 minutes. If you do not, your second check-in will determine the fare for the rest of your journey. Therefore, if you continue your journey during rush hour, you will pay the full fare.

Please note: this also works in reverse. If your first check-in was during rush hour, this rate continues to apply.

Hello. My personal card is linked to a bank account, first they took the monthly amount from me - 73.06 euros, then they returned it back. Can I see why this particular amount was calculated?

Dit kan je zien in Mijn NS (de website, niet de app), bij Betaaloverzicht.

Vanzelfsprekend kunt u ook even rechtstreeks contact opnemen met de klantenservice. Zij kunnen u ook vertellen waarvoor u dit bedrag moet betalen of waarom dit wordt teruggestort. Dat kan telefonisch: de klantenservice is 24 uur per dag bereikbaar op het telefoonnummer 030-751 51 55. U kunt er ook voor kiezen om met NS te chatten (druk op deze pagina op de knop Chat met NS) of een berichtje te sturen op Twitter of Facebook.

Dear Daniela.

You can see this in My NS (the website, not the app), under Payment overview.

Of course, you can also contact customer service directly. They can also tell you what you have to pay this amount for or why it is being refunded. This can be done by telephone: customer service is available 24 hours a day on telephone number 030-751 51 55. You can also choose to chat with NS (press the Chat with NS button on this page) or send a message on Twitter or Facebook.