How can I cancel the subscription of an accidentally subscribed free trial app?

Hello, i have accidentally subscribed to an app (AirBrush) that i don’t need subscription to. I checked on free trial of the app to see if it’s a good option for me or not. And when i realized it’s not for me, i canceled the subscription , but it keeps trying to charge me for the next trial which is for a year. Can you please help me with that, i don’t need the app and am not going to use the subscription, please help me cancel it. Thank you in advance

[Re-Titled by Moderator]