If you received an email that your AWS account is compromised and action is required from your end then you need to login into your AWS account and first change your root password. Then reply to the support ticket via AWS help dashboard.
You will receive a response from AWS requesting you to provide additional account details for verification. Provide the details and your limits will be removed.
If you don't reply to the email, your AWS account will remain temporarily limited for 5 days before being suspended.