Cyanogenmod is an awesome aftermarket Android ROM that you can put on your phone to get an experience closer to the stock Google experience. I use it on my Samsung phone because I don’t want to deal with Samsung’s weird bubbly UI.
All the people working on Cyanogenmod are phone nerds who aren’t getting paid, and even though their documentation is a lot better than you’d think, there are still a lot of questions that it’s hard to get straight answers to. Right before my last trip to Japan, I didn’t know whether or not Cyanogen supported GSM mode for my Verizon Galaxy S3 (i535 or d2vzw), so that I could use it with a B-mobile SIM in Japan.
This isn’t the sort of thing you can Google around to find out- you have to spend a lot of time working your way through arcane XDA-Developers threads and there’s a lot of outdated/self-contradictory information in those.
Anyway, here’s the deal. If you have a Verizon phone and you’re running Cyanogenmod 10 or 10.1 (CM10 or CM10.1), as long as the phone has a GSM antenna you can get it to work. Here is how:
Your phone should now be able to use GSM. In the case of B-Mobile you then have to go to Settings > More > Mobile Networks and add the B-mobile APN there.
This may work on other AOSP-based ROMs besides Cyanogen. The 4636 thing is a good thing to know about in general because it exposes antenna-related functionality that you generally can’t get to with the various Settings menus. If you can’t get GSM working on your Verizon global phone and are stuck, it’s always a good place to start.