Turns out that AT&T and Earthlink have some kind of arrangement which dates back to the early days of DSL. Since Earthlink uses AT&T's wire to my house, they've agreed to some kind of "no poaching" agreement. I would have to cancel Earthlink, wait ten days, order U-verse and wait for that to install. Time offline = about 14 days.
Nope. Since when do I not have free market choice? Because 40 years ago Ma Bell ran a chunk of copper wire to my house, I'm not able to buy what I want?