We hope you weren't planning to use your old-school iPhone or BlackBerry Pearl on AT&T's network for nostalgia's sake -- unfortunately, you're not going to get anywhere. As promised way back in 2012, the carrier has confirmed that it shut down 2G services on January 1st, 2017. If your phone only makes GSM calls and uses EDGE for data, you're stuck. The move won't hurt very many people (even basic phones have been using 3G and LTE for years), but it's hard not to shed a little tear for a technology that had been around for so long.
As it stands, you probably won't mind much given what AT&T has in store. It'll repurpose that newly freed spectrum for LTE, and the move will ultimately create more headroom for 5G wireless. Just as with the end to analog cell service, the small sacrifice you make now will likely pay much larger dividends down the road.
The shutdown is also a reminder of just how far mobile data has come since 2G hit the scene (in the US, at the turn of the millennium). EDGE was considered fine at a time when any mobile data was a relative novelty, and the most you did with it was check email or surf the most basic of websites. Now, even a modestly-sized app or photo download would absolutely crush 2G -- the modern mobile internet depends on speeds that are orders of magnitude faster. We can only imagine what it'll be like when 3G bites the dust and LTE is considered the baseline.