You best call the SBB Contact Center for this on 0848 44 66 88 (CHF 0.08/min.), from abroad: +41 51 225 78 00 (available 24/7, waiting times may occur).
A little side note: before renting a car in Lugano, kindly check with the Swiss car rental company if you are allowed to drive a Swiss registered car to Italy at all, or let them at least know your intention to do so. Car burglaries involving Swiss cars are not uncommon in Italy. Therefore, car rental companies may ask for a higher insurance, or for certain car types, they may even prohibit driving the car to Italy.