Wifi and cash

Switzerland doesn't use the Euro, it uses the Swiss Franc.

There are always multiple options for data plans on phones (assuming your phone is unlocked - check that). You can always buy a local SIM on arrival. Check with your carrier to see if your plan has an option for coverage there.

Yes, of course, you should always have cash. I always use credit cards where I can, but they won't be accepted everywhere (and you don't want to try to use one for something like a gelato). How much cash you carry depends on what you will be doing, where you are going, and other factors. Use your debit card from your home bank or credit union to pull cash from ATMs in Europe. Find out about the fees for that from your bank.

When is your trip?

Contact SPRINT for their international plans, check on their website.
You will need some cash for smaller items. Use the airport ATM when you arrive.
You will have two different currencies, Swiss Franc for Switzerland and Euros for Austria and Italy. Use up your francs when paying your hotel in Switzerland.

I don't know about cell plans, but I don't take any cash (or perhaps a $20 in my wallet). I just take a debit card and a credit card. (Just in case the debit card doesn't work, I can get a cash advance at a bank with a credit card.)
There are ATM's all over the place, at airports, train stations, banks. Still, since debit/credit cards are accepted at 95% of places, you might be able to get through a country without any cash at all.

Switzerland does NOT use euros, but rather Swiss Francs, abbreviated CHF .

You have two options for your phone:
1) Keep with your current provider. You would have to ask them if this is possible and how much.
2) Buy a new "Pay-as-you-go" SIM card for your phone in the first country you reach. This will work in all three countries.
This will only work if your phone is of the correct type (GSM) and is unlocked. If it is not GSM, then it won't work at all, neither (1) or (2) will be possible.
A new SIM card means a new phone number, from the country in which you bought the SIM card.

Yes, you need cash. You need cash for small purchases (street food, ice cream, ticket machines), anything under ~€20. Always check a place takes cards before ordering - to avoid embarrassment. And make sure you have told your bank you will be using your cards in these countries, so they don't block the transactions.

"I guess it would be Euro for all the 3 countries." - NO! Italy and Austria use the Euro. Switzerland uses the Swiss Frank.

Sprint has free international roaming data in Europe (though it is limited to "2G" speeds). Sprint's roaming plan is just like T-Mobile's: Free texting. Calls are 20 cents/minute. I have Sprint and just got back from Portugal. I had no need to make calls, but I used the data. It was slow. I had a Dutch Vodafone SIM anyway so just added 10 euros to the Vodafone SIM and got fast data for nine days - worth it to me. I could have survived with the slow 2G data, but I didn't need to. (Sprint also offers "day passes" for fast data that seem a tad expensive.)

I didn't have to call Sprint or do anything to use the international roaming, other than make sure my phone was in "global" mode for roaming. But my Sprint service is relatively new. If you are grandfathered into some old Sprint plan or something, you may want to contact them to confirm that your plan indeed includes the international roaming - I think all the newer plans do.

You might want to check out the advice here https://www.ricksteves.com/travel-tips/phones-tech and here https://www.ricksteves.com/travel-tips/money.

I typically use very little cash when I travel. It ends up that I typically only use cash for transportation and food from markets. On my last trip to Switzerland I was there 2 days and didn't use much of the 10CHF that I brought. Typically in Switzerland, local transportation is free with hotel reservations. You didn't ask, but not only does Switzerland use the CHF, it has a different adapter for electrical outlets. Often the hotel can lend you one, but I wouldn't count on it. I didn't know this for my first trip to Switzerland.

Thank you all.
I have notified the credit card company.
I checked with my bank on using debit card in the ATMs there. There is charge of $5 per withdrawal + 3% transaction fee! I guess it would be cost effective to just take some Swiss Francs and Euros along with me.

Thanks.

I guess it would be cost effective to just take some Swiss Francs and Euros along with me.

Check the exchange rate you are getting from your bank for Euros and Francs purchased before travel, versus https://www.xe.com/currencyconverter/. Still might be favorable to get in-country and avoid the security risk of carrying a lot of cash.

You might look into a new account as well. Charles Schwab has no-fees anywhere in the world, no transaction fee. Ditto your CC; Make sure you have one that does not charge an international transaction fee.

Time to find another bank/credit uinon with more favorble FX transaction cost. My CU passes on a 1% FX conversion fee (as a sepreate statement line item) i.e. Interbank + 1%. It's generally a good idea to have more than one ATM/Dbit card. Use your $5 + 3% account as your back up account.

The Swiss are very banking modern and credit cards are highly accepted. We used up our CHF buying nutcakes and chocolates at the Coop before departing. (Coop groceries accept credit cards as well as CHF cash).

If you think $5 and 3% is high, wait till you see what it will cost you to buy EUR (euros) or CHF (Swiss Francs) here in the US. Reports on this forum indicate that it costs about 7-10%.

There's nothing wrong with buying about $100 worth of CHF, if you want the convenience and assurance of arriving with some cash. But don't bring more than this, as it's just a waste of money. Simply use the ATM's in Europe, and take out a lot of CHF or EUR at a time, so you spread that $5 charge out. If you need more cash, make another withdrawal. If you have leftover cash, apply it to your last hotel bill.

Do find out your daily limit in dollars, and convert it to CHF and EUR, so you'll know the maximum amount you can withdraw.

If you are asked by the ATM if you want to guarantee the rate in US dollars, say no. Similarly, if you are using your credit card, always pick that it be charged in local currency, never US dollars. This is called "dynamic currency conversion," but a better name is "scam for the unwary." You will be charged a much worse rate than your bank will charge, and on top of that, since it's still a foreign transaction, you will still pay the 3%! I don't know about Austria or Italy, but in Switzerland, both bank ATM's and credit card machines often offered DCC.