App refund

I download an app called a while back and used the free trial, I did not like it all and tried everything I could to cancel my subscription before it charged me. I have been trying for so long, sending relentless emails to the app support page. Nothing, they have been charging me for going on a year!! I am furious. I cannot cancel this stupid app charge, I have no even had the app on my phone since I first tried the free trial . Plz help