In order to cancel your subscription you will need to go to your subscription status page. In your browser, press on the three line menu icon (top right hand corner) and press on the 'Subscriptions' button (direct link). There you will see the otion to cancel your subscription.
Simply deleting the app will not cancel your subscription or trial, and you will still be charged. Cancelling your subscription should be done by following the steps clearly set in the 'Cancel my Subscription' article.
Please bear in mind that you do need to cancel your subscription up to 24 hours before the 7th day of the trial or you will be charged.