It requires a deliberate action on your part to start a subscription including authentication. If this was a Free Trial that you authorized, you also saw the message to avoid charges you must cancel the free trail before the subscription start date. While you don't say if this was initially a free trial, I recommend users set a reminder a day before the renewal date to review the trial and make sure you want to continue. That way there is no chance you will forget as it is your responsibility to cancel. It makes no difference if you use an app or not, just like you can have a Netflix subscription and still be charged monthly even if you don't watch any of the shows.
Due to this deliberate action to start a subscription, in most cases all transactions in the App Store are final. At times Apple may provide a compassionate refund, but it should never be expected.