What should I do if my App Store refund request is denied?

I downloaded an app and there was an option to try the full version. I tried the app but did not like it so I cancelled it the same day the trial was ending. I saw that I was too late, and was billed for the subscription. I went to apple support and asked for a refund and selected "I did not mean to subscribe". I was denied a refund so I tried again and was denied also. I opened a case and talked with apple support and they said that I can't get a refund when it was a free trial before the subscription.

There has been several times when I forgot to cancel and I have always gotten a refund, even when I have paid for an app and used it, I still got a refund. What can I do to get my refund? It was 50 euros, so kind of a lot of money too:(

[Re-Titled by Moderator]