Skype is a good alternative, but you will need a Microsoft account and you will
pay per minute (not a lot, but still) unless you are calling a toll-free # or another
Skype account.
But if you do buy an unlocked phone and SIM card, you won't need Skype,
although you can still use it. If you peruse the Technology Tips subforum, you
will see lots of posts about European SIM's and other alternatives. You can
buy a SIM card with a certain amount of data and/or voice-SMS options.
You don't say just what you want to do (voice calls, SMS, internet access, or what).
Unless you plan to call people or establishments on your trip, Skype is not required.
And if you buy an unlocked smartphone with data, you can use other tools as noted
(or Whatsapp) to make free calls, voice or video.