Thank you for your request.
If you travel from Milano to Switzerland with an international train (EuroCity), the seat reservation is obligatory. You have to buy a ticket for the all trip with the reduction SwissPass. You will pay just for the italian part. It’s better if you do the reservation in advance directly on our website (www.sbb.ch/en) or at the phone with my colleague, if you have a credit card: 0900 300 300 (1.19.- CHF /min). You can also buy the ticket in all ticket office in Switzerland.
If you just travel from Domodossola to Spiez with a swiss train, the seat reservation is not obligatory. If you still want one, it’s 5.- CHF pro person and pro train. You can buy the ticket and the seat reservation on our website, in a station in Switzerland or at the phone.