[_Khaled_]

First add stock for admin chat..

pawn Код:

stock SendMessageToAdmins(color, const string[])
{
    for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(IsPlayerConnected(i))
        {
            if(GetPVarInt > Level)
            {
                SendClientMessage(i, color, string);
            }
        }
    }
    return 1;
}

CMD:a(playerid,params[])
{
    #pragma unused params
    //new pname[MAX_PLAYER_NAME]; //Your playername stock..
    new string[128];
    if(GetPVarInt > Level)
   { 
     if(!strlen(params)) return SendClientMessage(playerid,COLOR_ERROR,"Usage: /ac (Message)");

     //GetPlayerName(playerid, pname, sizeof(pname)); //Your player name stock..
     format(string,sizeof(string), "[ADMIN MESSAGE] %s(%d): %s",pname, playerid, params);
     SendMessageToAdmins(COLOR_RED, string);
    
     return 1;
     }
}

EDITED: to fit with your admin level defining