Since I have a Voip.MS account (VOIP), all I would do is load Zoiper on my cellphone, configure with my details and use Wifi on the phone to make or receive calls. Yes, I could receive calls made to my US phone number while visiting Switzerland and they would cost me a penny a minute.

Yes, not free but a penny a minute to the US or even cheaper (7/10's of a cent per min) to UK.

Calling this way back into Switzerland is 22 cents a minute to most mobile phones, but 2 cents a minute to landlines.

This service uses one of my US based telephone numbers.

I can only imagine what the call you are trying to make would cost.

ADDED: Using the hotel phone might cost even more as many hotels add charges for that too.