If you will be with friends who have access to cell phones, your personal need may be less than if traveling by yourself.
I can't imagine traveling anywhere without a phone these days. My experiences 2 months ago - just for starters:
1) A relative had a serious accident while I was in Europe. Other relatives contacted me immediately - direct call to my phone, they didn't even know I was abroad. I could monitor the situation easily from thousands of miles away via texts and calls.
2) My return flight was cancelled - major airline. I received a text message just as we were about to leave for the airport. Text saved us from making an unnecessary trip to the airport.
3) The automatic re-booking of my cancelled flight was not acceptable. I found the routing in an emaill via my phone minutes after the text - as I was standing in the train station ready to depart for the airport. I called customer service on my phone and had an acceptable alternative routing within 15 minutes of learning of the cancellation.
4) I booked a hotel for additional nights stay resulting from the cancellation and re-booking by phone.
5) We purchased special travel and site discount "Passes" for several cities we visited. These were not available in paper form - only by phone. I don't know if Switzerland expects the same level of tech availability as our locations.
6) "on the fly" decisions to visit a couple places that required advance booking. Easily done via phone and entrance with QR code display.
7) Of course, the standard travel phone usage these days - airline check-in via phone as soon as check-in opens, boarding pass held on phone, texts on gate changes, delays.
If you carry an iPad or lap top, that could be used in some of the instances above. I, personally, have stopped traveling with the iPad for personal travel and the laptop accompanies me only on business trips. Too heavy to cart the iPad around for use during the day - the phone can do all the iPad used to do for me.
We upgraded my husband to an iPhone a couple years ago. Prior, he had a no bells and whistles emergency type phone and we used my iPhone for our joint travel. He has commented multiple times since then that he can't imagine traveling these days without a cell. The expectations for phone access have multiplied in recent years.