I created an App several Years Ago that went under but linked it to AWS billing. I still get charged monthly

I understand your frustration with this situation. Unfortunately, closing an AWS account without access to the original sign-up email or account credentials presents a significant challenge. AWS has strict security measures in place to protect account access and billing information.

In your case, the best course of action would be to contact AWS Support directly. Even though you don't have access to the account, you should still be able to open a support case with AWS. You'll need to provide as much information as possible to verify your identity and ownership of the account, such as:

1. The AWS account ID (if you know it)
2. The name on the account
3. The billing address associated with the account
4. Any other identifying information you can remember from when you set up the account

Explain your situation in detail, including the fact that you no longer have access to the original email or account credentials. AWS Support should be able to assist you in verifying your identity and help you regain access to the account so you can properly close it.

It's important to note that even if you manage to close the account, you may still be responsible for any outstanding charges. AWS typically allows users to view past billing information and pay any outstanding bills for up to 90 days after account closure.

In the meantime, do not block the charges from your credit card or bank, as this could lead to complications with AWS and potentially affect your credit standing. Continue to work with AWS Support to resolve the issue properly.

If you're unable to make progress with AWS Support, you may need to consult with a legal professional who specializes in technology and contract law to explore your options for resolving this situation.
Sources
Close an AWS account - AWS Account Management
Understanding unexpected charges - AWS Billing
Understand billing for a closed AWS account | AWS re:Post