Yeah, I found that article early on. The thing is, mine is a G930T, branded for T-Mobile. From what I can tell ATT are simply being buttheads about allowing the use of non-ATT branded phones on their network. In any case, I'm using an MVNO that can use ATT or T-Mobile. I haven't been able to confirm it, but my hunch is that if I plop $5 down for a new TM SIM I should be back in business.
Frankly, I've always felt a little sore about using any ATT service. I have a grievance with them going back 15 or so years. This just reitterates my opinion that they suck, and I'll be happy to go back to TM.