[iGetty]

pawn Code:

#include <a_samp>
#include <zcmd>

new ChatOn;

public OnGameModeInit()
{ 
    ChatOn = 1;
}

public OnPlayerText(playerid, text[])
{
    if(ChatOn == 0) 
    {
        SendClientMessage(playerid, -1, "Chat is off.");
        return 0;
    }
    else
    {
        new string[128], pname[MAX_PLAYER_NAME];
        GetPlayerName(playerid, pname, sizeof(pname));
        format(string, sizeof(string), "%s (%d): %s", pname, playerid, text);
        SendClientMessageToAll(-1, string);
        return 0;
    }
}

command(chaton, playerid, params[])
{
    if(ChatOn == 0)
    {
        ChatOn = 1;
    }
    return 1;
}

command(chatoff, playerid, params[])
{
    if(ChatOn == 1)
    {
        ChatOn = 0;
    }
    return 1;
}

Simple.