office boy
From Longman Dictionary of Contemporary Englishoffice boyˈoffice ˌboy noun [countable] old-fashioned a boy or young man who does simple jobs in an officeExamples from the Corpusoffice boy• He was sent at the age of 14 to work as an office boy at the city railway station.• No more hiding from the post office boy who brought telegrams from the Somme each day.