I agree with the agent. your entity is being classified as a corporation so converting from an S to a C only changes the form that is to be filed. from the iRS viewpoint it is still a corporation.
Corporations
You will be required to obtain a new EIN if any of the following statements are true.
A corporation receives a new charter from the secretary of state.
You are a subsidiary of a corporation using the parent's EIN or you become a subsidiary of a corporation.
You change to a partnership or a sole proprietorship.
A new corporation is created after a statutory merger.
Limited Liability Company (LLC)
An LLC is an entity created by state statute. The IRS did not create a new tax classification for the LLC when it was created by the states; instead IRS uses the tax entity classifications it has always had for business taxpayers: corporation, partnership, or disregarded as an entity separate from its owner, referred to as a “disregarded entity.” An LLC is always classified by the IRS as one of these types of taxable entities.
