I want to unsubscribe from I Tunes. I have tried with my Iphone and cannot find the app but I get billed for it. The information Ive gotten so far on how do this does not work. Please would someone help me.

I bought an app but thought it would be billed through the App store but its billed through ITunes. When I pull up the app, it does not show the app I bought (a trial for two weeks) but I got billed for it this month and it will continue billing me. Can somebody tell me how to unsubscribe on an IPhone 8 plus? I was told to settings and find App Store and ITunes. I found the App Store but no I Tunes. Where is the Itunes in settings. The actual App for it does help either. Im dumbfounded! There has to be an easy way that I am not seeing. Thanks for the help