To cancel Amazon Music Unlimited, you can follow these steps:
On the website: Navigate to Amazon.com, open your account, select memberships & subscriptions, find your Amazon Music Unlimited subscription, and click on the cancel membership button.
On Android: Open the Amazon Music app, go to settings, select Amazon Music Unlimited Member, and cancel your subscription.
On iPhone and iPad: Open the Settings app, select subscriptions, find the Amazon Music subscription, and cancel it.
Via iTunes: Visit Apple's support site, log in to your account, go to billing and subscriptions, find Amazon Music Unlimited, and follow the on-screen prompts to cancel.