And that's why I'm on a $10/mo unlimited data plan, which naturally includes text messaging as "data".
Looks like that's no longer an option.
Anyone with the $5 plan actually has free access to any data connection; T-Mobile doesn't even try to separate it from the other data plans. The only problem is they don't officially offer it anymore.
I've heard some people have managed to convince customer service reps to turn it on from scratch by calling with their SIM in a feature phone and saying they want an old cheap data plan that would support their old cheap phone for doing simple online tasks.