RedBaron Hallo Thouroucki66 No, issued tickets can generally not be altered later. But depending on the ticket type and travel date (still in the future), a cancellation / refund may be possible. See here for more details: https://sbb-tickets.cc/en/help-and-contact/refunds-compensation/refunds-compensation.html
Danhiel Hello Thouroucki66 Some international tickets for France or Italy may be exchangeable to avoid refund fees, but you have to contact the vendor of the tickets. For SBB, see the bottom of this page: https://sbb-tickets.cc/en/help-and-contact.html Kind regards Daniel