Hallo @Nuria,
You can ask a refund of your ticket calling our Rail Service 0848 44 66 88 (CHF0.08/min) or you can use the following link: https://www.sbb.ch/en/travelcards-and-tickets/buying-options/online/faq/refund-request-online-ticket...
Have a nice day
SamanthaAd