[RoboN1X]

You are using ZCMD (CMIIW), There is already "params" parameter, which contain input from the command after space symbol (e.g. /admin <params>). You don't need to use strrest code placed on the command.
So just do this:

pawn Код:

CMD:admin(playerid, params[])
{
    if(!IsPlayerConnected(playerid)) return 0; // Player is not connected.
    if(Player[playerid][AdminLevel] >= 1) // Better check first if it's an admin
    {
        new sendername[MAX_PLAYER_NAME];
        GetPlayerName(playerid, sendername, sizeof(sendername)); // I'm not sure what are you going to use this at, But it might be replaced on function "RemoveUnderScore(playerid)" instead?
        if(!strlen(params))
        {
            SendClientMessage(playerid, COLOR_WHITE, "USAGE: (/a)dmin [admin chat]");
            return 1;
        }
        new atext[20]; // This only need 20 because the longest string, "Junior Administrator" length is 20
        switch(Player[playerid][AdminLevel])
        {
            case 1: atext = "Junior Moderator";
            case 2: atext = "Moderator";
            case 3: atext = "Lead Moderator";
            case 4: atext = "Junior Administrator";
            case 5: atext = "Administrator";
            case 6: atext = "Lead Administrator";
            case 7: atext = "Owner";
        }
        format(string, sizeof(string), "[%s] %s (%d):"COL_WHITE" %s", atext, RemoveUnderScore(playerid) /* Isn't this supposed to be "sendername"? */, playerid, params);
        SendAdminMessage(COLOR_NICEGREEN, string);
    }
    else SendClientMessage(playerid, COLOR_WHITE, "You are not an admin!"); // or "return 0;" here
    return 1;
}

I've also corrected some code, so only admin can send it, and optimized the variable usage. Although it's not tested yet, but i'm sure it will work.