The point I was going to make in the article below was it might be a good idea for you to have a “real” Japan phone number (as opposed to a VoIP number) if you’re visiting Japan, but then I realized it is kind of a moot point. Japan is very strict in giving you phone numbers and, as far as I know, PAYG SIM by b-mobile is pretty much the only option for short-term visitors to get a local number—and it ain’t cheap and is definitely not for everybody. Except for it, it is practically impossible for you to get a local number unless you get help from someone already residing in Japan.
I am publishing the article anyway, though…
Suppose you are going to visit a foreign country. Your phone carrier (e.g., AT&T, Spring, Verizon, etc.) may offer international roaming packages. It is almost guaranteed to cost you more (probably wayyyyy more) than purchasing a prepaid SIM card for your destination country, but you might still choose it thinking it is a hassle-free option. After all, you can just bring your usual cell phone and you should be all set; you won’t have to deal with all that technical complexities like having a SIM-lock free phone ready or swapping SIM cards.
That is exactly how an American friend of mine felt, when he came to Japan for a visit this past May. He is an AT&T subscriber and opted for its Passport international roaming service. Did it work for him? Not really.
The biggest problem was that he wanted to receive (conventional) phone calls from his friends in Japan even when he was on the road, away from his hotel where he had reliable Internet connection—but he only had his usual US phone number for them to call, which could cost them dearly. If it is a regular US number, you can actually call it for free if you know how, but that’s not common knowledge among ordinary Japanese people.
Since he had a smart phone (or more specifically, an iPhone), he could have signed up for an Internet phone (or VoIP) service in Japan and get himself a local phone number for people in Japan to call. Or he could have gotten a Skype Number for the same effect. Would it have helped, though?
Not really, at least not in this particular case. This is because he had sporadic connection to the local mobile network. I do not know if that is because he messed up somewhere somehow, or because the service was inherently unreliable. But whatever the case may have been, it pretty much made it impossible for him to contact people on the go via online methods; this is actually the very reason why a real cell phone number would have helped.