how I can request a refund

Good afternoon, today I received a letter saying that I have to pay an amount higher than I have to pay. I have two situations, the first one I went through NS, well, I needed to go through Kampoon through blue. well, at that moment I had a subscription to a free month in Greenland, I made a check in at 16:38 and there is no NS in Campon, well, I was deducted 20 € because I did not use NS. the second case, I saw off my grandmother and she had heavy bags, we were late for the train, I went with her to carry things and the train closed and I did not have time to get out. I asked your colleagues, they said there was nothing wrong at the nearest stop, I should get off and go back. and unfortunately I went back and did an check out and still the payment was debited. I read on your site that I can stay for 6 hours and the payment will not be charged and I was much less. How can I request a refund.