My daughter bought Swiss francs and she didn't spend it all, now she is in Austria, where can she change the Swiss francs (CHF) to Euros (EUR)?
You should try any big banks! they will be able to do it. If you have the receipt of purchase for those Francs (I doubt it), it will be a plus as it clearly shows that you probably have done it for travel purposes.
I am not sure about the Weschels (Cambio/Bureau De Change). If the shop is too small, they might not have the CHF to Euro/USD/GBP facility. Try bank or a hot touristy spot. Airport should be the ideal place if everywhere else turns out to be blank.