Apple just charged me for apple itunes music subscription but I never ordered it.

I believe a trial membership was made the default action when setting up devices or similar actions. This then rolls over to the paid version after 3 months. This is why people need to read the every option menu that appears when setting up something.

Manage your Apple Music membership - Apple Support - https://support.apple.com/HT204939 - "Learn how to change from an Individual membership to a Family membership, turn off automatic renewal, or join Apple Music later."

Is this from an email, and if it is are you sure that it's a genuine email from Apple and not a phishing email trying to get your account and payment details (Apple Music seems to be a current favourite for phishing emails) ?

Phishing and similar emails : Phishing & Other Suspicious Emails

Phishing emails : Identifying fraudulent "phishing" email - Apple Support

Genuine iTunes emails : Identifying legitimate emails from the iTunes Store - Apple Support

Viewing your account's purchase history : See your purchase history in the iTunes Store - Apple Support (on an iOS device you can view the last 90 days purchases via http://reportaproblem.apple.com)