I’m glad I found my answer in this older thread. I have been using my Fairphone 1 in the United States (Michigan) for a year or two now. My carrier is AT&T, and I believe I am on the 2G GSM EDGE network.
A few weeks ago (Feb 2016), I received the following text message:
AT&T Free Msg: Thank you for choosing AT&T! We appreciate your business. Due to planned network upgrades your device will no longer work on the AT&T network after December 2016. To avoid service disruption upgrade to a 3G or 4G LTE device as soon as possible. For more information visit AT&T Customer Support
The link indicates they are discontinuing 2G service. With a little digging, I discovered they are focusing on HSPA+, 3G and 4G LTE. I also found the AT&T Mobility page on Wikipedia which specifies the network’s supported bands and protocols.
Well, thanks for the info! It looks like I will soon have a Wi-Fi-only Fairphone.