Hello sanascimento
Yes, a Swiss Travel Pass can be exchanged, provided
- the exchange is done before the STP’s first day of validity
- It was bought with SBB
The exchange can be done by phone (+41 848 44 66 88) or at any SBB Travel Office.
However, I wondered if it makes sense to exchange your STP. Wouldn’t it be an option to buy a Saver Day Pass for day 5, or even a single ticket provided the amount to be spent does not exceed the average cost per day of a 6 days pass?
https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/day-pass/saver-day-pass.html
Should you have bought the STP with an agency, for example Klook, kindly seek advice with them concerning an exchange.
Kindly yours,
Roland