AWS payment issue

Hello.

I recommend that you sign in to the management console and check your invoice.
https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/getting-viewing-bill.html

If you do not remember the AWS service for which you are being billed, there is a possibility that your AWS account has been accessed illegally, so I recommend that you change the password of the root user of your AWS account and suspend the IAM user.
https://docs.aws.amazon.com/IAM/latest/UserGuide/root-user-password.html
https://docs.aws.amazon.com/IAM/latest/UserGuide/id_users_manage.html#id_users_deactivating

If you have billing issues, you can also contact AWS Support by opening a case under "Account and billing".
Inquiries under "Account and billing" can be made free of charge.
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html

It's possible you still have a service running and your free-tier has expired, or you had some IPv4 addresses active that are now being charged.