Why was I charged for my free trial?

So I downloaded a photo editing app and it was advertising a free trial subscription for their yearly plan directly on the app. When I tapped on “start my free trial” the purchase Authenticator for the iPhone X popped up for face id. I double press the power button, and use the app for a bit. I wanted to renew my hulu subscription to find that all my money was gone. Instead of some sort of 7 day free trial it charged my account for the subscription. Imidiately charged my account around 40 dollars. I was wondering if there is a way to get some sort of refund of the subscription I accidentally purchased? I need help!