Help me, please /a chat

[SA:MP]

Help me, please /a chat

So, I'm trying to make an admin chat, basically admins can speak with eachother using the command /a [text]

But, I got this command:

pawn Code:

CMD:a(playerid, params[])
{
    new sendername[MAX_PLAYER_NAME], result[128], string[128];
    if(!(PlayerInfo[playerid][pAdmin] >= 1)) return SCM(playerid, COLOR_GREY,"You are not authorized to use this command");
    if(sscanf(params,"s[128]", result)) return SCM(playerid, COLOR_GOLD,"USAGE: /a [chat]");
    else
    {
        format(string, sizeof(string),"*%d Admin %s: %s", PlayerInfo[playerid][pAdmin], sendername, result);
        SendAdminMessage(COLOR_GOLD, string);
    }
    return 1;
}

Every time I type for example: /a hello, or anything, I'm getting always this message: "USAGE: /a [chat]", any help, please?

Source: Help me, please /a chat