When we get our phones, we have to do a *228 option 1 to activate, then *228 option 2 for roaming capabilities. It updates the PRL file. (Preferred Roaming List).
Actually, there's an easier way to do both at once. You can dial *22899 and you're set.
This isn't vital information for regular DX users, but vital for root users and regular users who have done a factory reset on their phones.
When you do a factory reset, you have to update your PRL. When, as a root user, you install a fresh rom, wiping data, cache and system, it's just as if you're starting from scratch. If you don't update in either situation, then you will have very poor call quality. Trust me, I was getting complaints from people on the other end of my calls. When I installed a fresh rom, updated from eclair to froyo or did a factory reset, I didn't know to update the actual phone! It sounded awful
So, whenever you get a replacement phone from VZW, you have to do the same thing. My daughter needed her Incredible replaced. She sounded terrible until I told her to do a *22899. Muuuuch better after.
So, yeah, keep updating your phones. You'll only benefit from doing it!
Happy Thanksgiving!