interlocutor
noun [ C ]
formal uk/ˌɪntəˈlɒkjʊtər/ us/-ṱɚˈlɑːkjəţə˞/someone who arranges a deal or agreement between two organizations or groups, or who speaks on behalf of an organization or group of people:
The vast majority of our interlocutors from the retail sector indicated that they would not be interested in parallel trade, for fear of spoiling long-term relations with their manufacturers.