If he has a Verizon iPhone 4, it is CDMA only. Almost all the networks in Europe are GSM. That phone won't work there. Do you know why he can't get WiFi? Is it a problem with the phone? Or is it that he just doesn't have access? If he had WiFi access he could use something like Skype or Viber to make calls. If he has no way of getting WiFi, he will probably need to pick up a prepaid phone.