Who should say Aqamat in office prayer room where there is no permanant Moazzin and Imam?

It is the moral right of a person who calls out the Adhaan to also call out the Iqaamat. This is mentioned in the Hadith. Once a Suda’ie person called out the Adhaan. Hadhrat Bilaal [radhiallaahu anhu] was about to call out the Iqaamat. Rasulullah [sallallaahu alayhi wasallam] said, ‘The Sudaai’e brother called out the Adhaan, and whosoever called out the Adhaan should call out the Iqaamat.’

If the person who called out the Adhaan permits another person to call out the Iqaamat, that is his moral right.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai