Although you get a 3-month free trial, how do you ensure Apple doesn’t charge you after if you don’t want to?
Simply go to the Apple Music app, tap the avatar on the top left corner, choose “View Apple ID”, type your password if prompted then choose “Manage” under “Subscriptions”.
Here you’ll be able to “Turn off automatic renewal”.
This will keep your free 3-month trial but will not charge you automatically at the end.
Should you change your mind, you can always tap on the subscription option that suits you to continue using the Apple Music service.