Hello and good day.
You did not provide any specific details of seats in your enquiry. Are these seats or tickets?
This may vary depending on the situation. Unfortunately, as a matter of fact, we cannot exchange tickets for journeys in Switzerland. In this case, the only option to consider is to make a refund request.
If it concerns an international ticket, tickets can also be exchanged or refunded depending on the ticket conditions.
If either of the information given is correct, I would recommend that you get in touch with us with these tickets either by telephone on: 0848 44 66 88 (CHF 0.08/min.) or from abroad +41 51 225 78 56, via live chat or directly at a staffed SBB counter.
I wish you a pleasent Day,
Greeting SamuelW