I recently signed up for an SBB Half-Fare Travelcard, but I have left Switzerland permanently on December 31st, 2024. As I will no longer be able to use the Travelcard, I would like to request a refund for the unused portion. Could you please advise me on the steps I need to take and the documents required to process my request? If needed, I can provide proof of my deregistration from Switzerland.