ATT got version 18.1 a month or 2 back. Supposedly solve some issues. There is another thread here about that one. Here is a bit of info regarding carrier updates. http://support.apple.com/en-us/HT201270
And from Verizon.
And from Verizon.
Carrier settings updates are small files that are installed on iOS devices. The Carrier settings include updates to Access Point Names (APNs), MMS Settings, features such as tethering and default apps such as Stocks, Maps, and Weather. Having the most up to date Carrier Settings is recommended for the proper functionality of the device.