What is Apple Arcade? Why need to pay even I’m not subscribed

Apple Arcade is a collection of video games you can play on your iPhone, iPad, Mac, and Apple TV. See here: link-> Apple Arcade - Apple

If you accepted the trial, it auto renews into a paid subscription.

You can cancel it from your Subscriptions at any time: link-> How to cancel a subscription from Apple - Apple Support

Click the Report a Problem link in the email.

If you bought an apple product you got 3 free months. if you did not cancel the subscription then it started charging you.