He doesn't need a CF to buy a phone, only an ID. Vodafone is the best for this. I've had several friends come for a month or longer and decided to buy a Vodafone SIM card to slip into their unblocked phones. Just an ID, that's all. If you trust him to not lose his passport, just take that with him to the store to buy a pay-as-you-go phone. Yes, all incoming calls are free. He will be able to call long-distance to you as well. With some companies, he can choose to make the US his "preferred" country and it gives a discounted rate of something like €.15 per minute or so.