I tried it from a Movistar fixed line.
First, just dialing <4242>
" el número que Ud. marcó no existe"
Then tried <*4242>
First attempt:
“La configuración no se modificó”
Subsequent tries:
“Chile Atiende te da la bienvenida”
Followed by a long menu of Chile Atiende consultas, Pensiones, Salud etc etc.
Maybe it works better from Cellphones…