Up until recently T-Mobile refused to let people opt-out of receiving text messages, regardless of what steps you were willing to go through. The only reason they changed their policy was because of a class-action lawsuit that was filed against them.
Ah, yeah, that's what I was talking about. I didn't realize there was a suit that changed their policy. I talked to them fairly recently, and their reps denied the possibility of opting out.
I'm guessing not receiving text messages at all is also not an option for some people. Being able to whitelist numbers from which you can receive messages would be much better.