Imagine coming home after an incredible tour through Italy and being immediately welcomed with an outrageous phone bill (not fun). Just because you can make phone calls in a foreign country doesn't mean it's covered in your plan. Call your carrier to find out your options; some offer totally free international roaming, but it's something that needs to be activated. To be safe, you can also leave your phone in airplane mode and use WiFi to communicate (this is also where printing the reservations/addresses comes into play).