of service to someone, be

be of service (to someone or something)

To help, serve, assist, or work for someone or some group or organization. Good evening, sir, how may I be of service? My father was of service to that company for over 50 years, and the only thing they gave him at the end was a cheap watch.
See also: of, service, someone

of service to someone, be

Help someone, as in How can I be of service to you? This idiom uses service in the sense of "supplying someone's needs." [c. 1700]
See also: of, service