Money back

If you didn't cancel the subscription more than 24 hours before the free trial ended you would automatically be charged. To prevent further charges you should cancel the subscription:

Manage your Apple Music subscription - Apple Support

As to a refund, strictly speaking all purchases are final (after all, you can't very well return them): please see this page for information on requesting a refund: Request a refund for an App Store or iTunes Store purchase - Apple Support

However Apple have been known to be sympathetic in cases of actual error, so it's possible that they may allow you a refund as a one-off concession: but please be aware that they are under no obligation to do so: go to iTunes Store - Contact Us - Apple Support

Alternatively go to the page suggested in the Help page linked to above: Report a Problem

About payment card authorization holds from the App Store or iTunes Store - Apple Support

You may have seen an authorization hold from a card payment. This is not a subscription fee, but a payment method test. It will be undone or returned when cleared.

Purchases and subscription fees will be listed in the purchase history for your Apple ID account:

See your purchase history in the App Store or iTunes Store - Apple Support

If you see 'itunes.com/bill' or an unfamiliar charge on your statement - Apple Support