Hallo ivy1,
Thank you for the request.
If it is a ticket for a trip within Switzerland, you can have it refunded using the form:Refund on tickets in Switzerland | SBB help & contact
However, if it is an international ticket you must contact us by phone:
Tel. 0848 44 66 88
(CHF 0.08/min.)
(available 24/7, sometimes you may be required to wait)
or if your calling from abroad:
+41 51 225 78 00
I wish you a lovely day
Kind Regards MelanieD