representative, agent
緊急の時は私の代理人に連絡をとってください。
In case of emergency, please contact my representative.
私が町を離れている間、弟を私の代理人にした。
I appointed my younger brother as my representative while I was away from town.
代理人ではなくあなた本人が来てください。
Please come in person, not through a representative.