Samsung SCH-A790 / SCH-A795 / IP-A790

As pointed out in an earlier reply, you have to manually switch the phone to the proper mode (i.e. GSM or CDMA). If that's not the problem, there's another possibility, which was a problem with my phone. Specifically, Verizon has to register the SIMM card with Vodaphone, which handles their GSM service. Mine had not been registered. When I called, it would simply hang. I had to call from a landline in Italy and was on the phone for about 1/2 hour (nice). Anyway, the tech had me take the SIMM card out and read the number to him. He then input the number into the system and within about 30 minutes it worked fine (and I mean really fine as I've mentioned in an earlier post).

The problem I've found is that Verizon support personnel are a little unfamiliar with this phone. You have to enable the phone for international long distance (one step in the process) and they have to register the SIMM card. When I called, before leaving, they told me all was well, but they were apparently just looking at the international long distance service and not the SIMM registration. Be sure to ask for the global phone service techs when you call.

Incidentally, I used the phone in Venezuela last week. Although that is a CDMA service, it worked just fine in some pretty remote spots.