//Make a separate script inside you RACTER prim and then
//use this code to enable or disable speech for your NPC.
//Script name you are controlling is CaSe Sensitive.

//Use "chaton" or "chatoff" in local chat to toggle.

integer listenChannel = 0;

default
{
    state_entry()
    {
    llListen(listenChannel,"","","");
    }
    listen (integer channel, string name, key id, string message)
    { 
    if (message == "chatoff")
    {
    llSetScriptState("Brain", FALSE);
    }
    if (message == "chaton")
    {
    llSetScriptState("Brain", TRUE);
    }  
    }
}