[Correlli]

Look for the 'return 0':

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
  // your commands.
  return 0;
}

and replace it with your message:

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
  // your commands.
  return SendClientMessage(playerid,COLOR_GREY,"Sorry Command not found in NatiosnRoleplay database.");
}