When you signed up for Shudder with your Amazon billing information to start a subscription on your Fire TV, you can only manage the subscription on the Amazon website. To cancel your Shudder subscription on Amazon.com:
- Go to https://www.amazon.com/appstoresubscriptions
- Find the Shudder subscription and select 'Actions'
- Choose 'Edit payment information' -> 'View billing history' -> 'Cancel your subscription'