The method to stop using AWS

Hello.

You can cancel your AWS account by following the steps in the document below.
Your AWS account will remain for 90 days after you cancel, but it will become completely unusable after 90 days.
https://docs.aws.amazon.com/accounts/latest/reference/manage-acct-closing.html#close-account-procedure

Operations must be performed as the AWS account root user, not as an IAM user.
Root users can sign in using the steps in the document below.
https://docs.aws.amazon.com/signin/latest/userguide/introduction-to-root-user-sign-in-tutorial.html

You can also search for active services in your AWS account by following the steps "Confirm you have terminated all active resources" in the document below.
I think it's a good idea to use this procedure to search for resources, compare them with the invoice, and delete any resources that are incurring costs.
https://repost.aws/knowledge-center/check-for-active-resources