Service (diakonia) in Romans 12:7 is not ministry in the sense of occupying a position of clerical authority. That’s an anachronistic interpretation from the more recent sense of a bureaucrat serving the needs of a king or a nation, or a congregational leader serving the needs of his congregation.

Diakonia, as used in the Bible, refers to serving without implying any kind of authority relationship over the one being served. It is much more likely to imply being under authority than being in authority.