How can I cancel a expired subscription?

Hi guys👋-1F3FB;! I made a purchase like a few months ago and it was not on purpose. I was playing my game, this ad came up and bang 💥I began a 7-Days free trial👌-1F3FB;. And then I deleted the app cause I didn’t like it and I thought that the pitchise was gone🤔. Another month after I downloaded another app and made the same mistake🙍-1F3FC;♀. I deleted the app again and I had the same thought. Two months ago I stared having trouble with updating my apps. And when I went on my purchase history I saw that I own 15€ for something I didn’t use. I tried to cancel it but I couldn’t. I need help. Thanks. 🎀