Noted by The Verge, your original iPhone will no longer work on AT&T’s network. The carrier decided that on January 1, 2017 it would begin shutting down its 2G network in order to free up spectrum for new technologies such as 5G.
Owners of the iPhone 2G will be unable to receive/send calls or texts, and won’t have access to AT&T’s data network.
With that being said, AT&T’s minimum requirements is now 3G WCDMA (UMTS) HSPA 850/1900 Mhz Band 2 and Band 5. Devices that don’t support those bands will also need to be upgraded to a newer device. “You may be able to keep your current rate plan when you upgrade your device, however it is possible you will need a new one,” AT&T says.
As most of us know, the original iPhone lacks a 3G chipset and runs purely on the 2G network. AT&T will send you a notification if it detects your device is still running on the 2G network. The carrier urges any customers still running a 2G device to visit an AT&T store to upgrade to a 3G or 4G LTE device.