[[MG]Dimi]

pawn Код:

if(!strcmp(cmd, "/a", true))
{
    if(pInfo[playerid][Admin] < 1) return 0;
    new text = cmdtext[4], adminname[24];
    if(!strlen(tmp)) return SendClientMessage(playerid, COLOR_YELLOW, "USAGE: /a [text]");
    GetPlayerName(playerid, adminname, sizeof(adminname));
    format(string,sizeof(string),"Adminchat (%s): %s", adminname, text);
    MessageToAdmins(purple,string);
    return 1;
}

stock MessageToAdmins(color,msg[])
{
    for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(IsPlayerConnected(i) && pInfo[i][Admin] >= 1) SendClientMessage(i, color, string);
    }
    return 1;
}

This is how I would make it. Should work. Untested. Also your statements are saying if player's level is 0 or higher which means it includes 0. I guess the lowest your admin level is 1, not 0 so I changed script according to it. Also I think you can't make public callback for function. Use

pawn Код:

stock

Have fun. Post if any errors