StopVoiceSending 

Namespace: SynicSugar.RTC

public void StopVoiceSending()

Description 

Stop local user sending voice chat.
If UseOpenVC is true, toggles setting state to send vc. If false, a thread for PushToTalk will stop.

using SynicSugar.RTC;
using UnityEngine;

public class VCSample : MonoBehaviour {
    public void StopVC(){
        RTCManager.Instance.StopVoiceSending();
    }
}