The room telephone is not working.
te-LE-fo-no — four syllables, stress on the second.
If the in-room telephone does not work, this is important to report — it is your primary means of contacting reception in an emergency.
'Telefono di camera' = room telephone. 'Non funziona' = does not work. A non-functioning room phone is more than an inconvenience — in an emergency, it could be critical. Most hotels can reroute calls or provide an alternative contact method.
Non sento il segnale nel telefono di camera.
I cannot hear a signal in the room telephone.
The line may be disconnected rather than the phone being broken
Non riesco a chiamare la reception.
I cannot reach reception.
The practical consequence — what you need to fix
Posso avere un numero di cellulare per contattarvi?
Can I have a mobile number to contact you?
Practical workaround if the telephone cannot be fixed immediately
Modern Italian hotels are increasingly replacing traditional room phones with tablets or apps that allow guests to communicate with reception. However, in an emergency, a working telephone is essential. Always test the phone on arrival and ask for a mobile contact number as backup.