find My account

Let's assume the email address that the billing invoice was sent to is the root user for your account. If so then login to AWS Console with that email address https://console.aws.amazon.com/

If you have forgotten the password then you can reset it by following these steps https://docs.aws.amazon.com/signin/latest/userguide/troubleshoot-forgot-root-password.html

If you can't login to the account then see the "Billing or account support" section of https://aws.amazon.com/contact-us/ for more help.

I recommend to review this article that might be helpful https://repost.aws/knowledge-center/charges-from-unknown-account

Important: AWS Support can't discuss any account-related information if account security isn't verified.