1/18    If I have an AT&T Nokia GSM phone, can I use it in Japan?  If
        so, I assume that if someone in Japan wanted to reach me, they
        would have to call my number in the US.  But, can I replace
        the SIM card and get temp service in Japan so that people in
        Japan can reach me?
        \_ Unfortunately, Japan uses a Japan-only protocol called UMTS
           so your phone won't work there. Korea is also screwed up
           in that they use CDMA. You have the U.S. to thank for that.
           You can find out more info on each country at
           http://www.attws.com/business/plans/international/disc_roaming.jhtml
        \_ Then, there is China, who is trying to be different:
            http://www.tdscdma-forum.org
        \_ If you are in Japan, you are out of luck completley.  Even if you
           are traveling to GSM area such as China and Europe, you need to
           make sure two things: 1. Your phone is so-called tri-band GSM
           phone.  The reason behind this is that everywhere else in the
           world uses frequency 1800 MHZ, but here in USA, the military
           occupied 1800 MHZ and not willing to release it.  As result,
           USA's GSM uses 1900 MHZ.  Typically, you need to make sure your
           GSM phone has ability to use 1900 MHZ (given, considered that you
           bought in USA) and one of the frequencies: 1800 MHZ or 900 MHZ,
           with 900 MHZ as remote second choice.  Most tri-band phone uses
           all three (1900/1800/900) frequencies.
           2. Before you take off, call AT&T as ask them to unlock your
           phone.  Most of the GSM phones sold in USA are locked to a
           specific carrier, thus, you won't able to use other SIM card.
           They could easily unlock the phone by sending you some weir
           SMS or something like that.
           \_ No can do. AT&T refuses to provide the network unlock codes
              because "AT&T works overseas". That's just AT&T bullshit.
              You can get your phone unlocked at many Chinatown shops.
              I got mine unlocked at the AT&T store in Cupertinio Village
              for about $20. If you go with T-Mobile or Cingular, they'll
              do it for you.
           Then, it's just matter of buying a pre-paid SIM card at whatever
           airport you arrived in.  Very convenient.
                                -GSM/GPRS fan
              \_ All this talk, but it won't work at all in Japan? -op
                 \_ No, it won't.  The first response already answered your
                    question, but, since you are either illiterate or a
                    chowderhead (that's a technical term), I'll explain it in
                    simple terms you can understand.  Of course, that still
                    won't help if the problem is the former.  You can't use a
                    GSM phone in Japan for the same reason you can't use a GSM
                    phone with Verizon or Sprint service here in the US.  The
                    hardware radio in your phone uses a different technology
                    that operates at a different frequency and uses a
                    different protocol compared to the hardware radio of a
                    Verizon or Sprint phone (various flavors of CDMA) or a
                    Japanese phone (UMTS).  Get it? - wielder of the cluestick