Hello Rauchouvik63
Tickets to Italy are an exception, they could be exchangeable. You can read the conditions here:
https://sbb-tickets.cc/en/tickets-offers/tickets/europe-interrail/conditions.html
If you have a non-discounted ticket (standard), you can try to load it in the Trenitalia app and choose the new date in the app.
Please note that, after carrying out an exchange on www.trenitalia.it, a ticket to Italy purchased in Switzerland can only be exchanged via Trenitalia and generally cannot be refunded.
If it is not possible, call the SBB Contact Center or visit a ticket office in Switzerland:
Tel. 0848 44 66 88
(CHF 0.08/min.)
(available 24/7, sometimes you may be required to wait)
Kind regards
Danhiel