Amazon prime you mean? Came her to complain about that. In the prime app, there is a button that disconnects your device from the account, but it just logs you out. You need to go to the website to manage your subscription, and after a few screens and then there is a button you need to keep pressed down for several seconds before it works. Keep reading the button labels because the default button will keep you subscribed. Whoever built/ordered that knew it was immoral.
There's no automated way to do it. You have to send a message to customer service asking to have your account closed.
You may need to be persistent. It's been a while, so maybe this has improved, but they hassled me a lot in the process when I did it.
I did this last week, it was pretty easy to find in account settings. They allowed me to delete my whole account, and required an email confirmation. On the other hand, I hadn't used it for much, and I live in Canada, so I can't speak to what others will see.