Here's a quick video demonstration on how to cancel your Apple Music Subscription.
I followed Apple's instruction from their website: https://support.apple.com/en-us/HT204939
On your iPhone, iPad, or iPod touch:
1. In the Music app, tap your profile icon in the upper-left corner.
2. Tap View Apple ID.
3. Under Subscriptions, tap Manage. If you have more than one subscription, tap Your Membership (Apple Music Membership) to see your membership options.
4. Under Renewal Options, turn off Automatic Renewal. Confirm your selection, then tap Done.
5. Tap Done to return to your Account screen, and then tap Done to return to the app.
This was performed on an iPhone 6+ iOS 9.1 Beta on 10/25/15.
Thanks for watching!