Cell phones that support the GSM Wireless system (Global System for Mobile Communications) work in most places around the world these days. Most cell phone providers do provide GSM-capable phones, although you may have to call your service provider to have the technology “turned on” or “unlocked”. You can also rent GSM-capable phones.
In order to make phone calls or use data you must activate an international plan. Call your cell phone provider to see what they offer and make sure to check about expected cost, options and limitations. Depending on your provider’s service package, you may be charged for both outgoing and incoming phone calls.
You might consider buying a local pre-paid SIM card to switch out – remember you will have a local number then. For more information about using European SIM cards in your smartphones check out Rick Steves’ blog post.