If you subscribed on the AMC+ app for Fire TV, Firestick or Fire Tablet

  1. Go to https://www.amazon.com/appstoresubscriptions and sign in with your Amazon account information.
  2. Find the subscription for AMC+, and select Actions.
  3. Choose "Cancel your subscription"

If you subscribed by adding AMC+ to your Amazon Prime Video account

  1. Go to https://www.amazon.com/myac
  2. Under Prime Video Channels, find AMC+
  3. Select Cancel Channel and confirm

    For more details, see Amazon's guide