You’ll need to go into your iPhone's Settings > [your name] > iTunes & App Stores > Apple ID > View Apple ID > Subscriptions > 1SE > Cancel Subscription.
This is the only way Apple allows subscriptions to be canceled.
FYI: Canceling doesn’t provide a full refund. It only stops renewal.
Please talk with Apple for a refund of the remaining time on a subscription.
Here’s a helpful Apple article on it: https://support.apple.com/en-us/HT202039#subscriptions