An individual is one person under the law. A corporation or an LLC (even a single member LLC) is a different person. Even if the beneficial ownership regulation has infused your bank with knowledge that an individual is the sole shareholder or member, you would not process an IRS levy in the name and SSN of the individual against the legal entity.
You have added information that indicates the legal entity may be a sham. For your own purposes, you need to begin unwinding the relationship; e.g. tell the customer the legal entity must close the account.