ToggleReceiveingFromTarget 

Namespace: SynicSugar.RTC

public void ToggleReceiveingFromTarget(UserId targetId, bool isEnable)

Description 

Switch Output setting(Enable or Mute) of receiving from target user on this Session.
If targetId is null, effect to all remote users.

using SynicSugar.RTC;
using UnityEngine;

public class VCSample : MonoBehaviour {
    public void Start(){
        RTCManager.Instance.ToggleReceiveingFromTarget(null, true);
    }
}