Generally no. Seat reservations cannot be refunded or exchanged. Special conditions apply to trains subject to a surcharge.
There is an exception if the rolling stock used for the train changes at short notice and your reservations are made invalid. Ask the train crew to provide you with written confirmation. You can obtain a refund of the CHF 5 at the ticket counter or you can exchange it for a promotional code online (to be used for any service when making your next online or mobile booking).