Thank you for your request.
To reserve a seat, you can prepare the desired route in the SBB Mobile app. Tap on “Tickets from CHF XX.XX”. The ticket options will then appear. Further down, click on “More tickets and reservations”. If seats can be reserved, the option “Seat reservation” appears and you can book the desired seat directly via the app. Alternatively, you can contact the SBB Contact Center by phone for advice or to reserve a seat at the following number +41848 44 66 88 (CHF0.08/min). If you are calling from abroad and the above number does not work, dial +41 51 225 78 00.
I wish you a happy new year.