In app purchase cancellation

Hi I accidentally subscribed to in app purchases on “magic tiles 3” and I no longer wish to cancel it. It’s a total of €2.99 monthly and I don’t want to be charged for it, I don’t frequently use the app and have no use for the purchase I subscribed to accidentally. Can you give me guidance on how to stop the subscription and the money being taken out of my account? Kind regards, Lauren.