Sossoulie81 I am a bit confuse because the cost should be free within Switzerland (due to STP) and the CHF 42 should be related to the ticket and seat reservation that related for Italy (please confirm it that make sense)? Does your comment advise me to buy ticket or reserve seat from other official website or no action required after we have paid the CHF 42?
The 42 CHF is indeed for the Italian part of the trip (Chiasso - Milano). You will also get a reservation, but that will be all the way to Luzern. So if you book this you are all set.