How does one prevent SMS spamming?

In the last few days I have been getting SMS spam from outfits that purport to represent fund555.com, wire600.com, pay600.com and money600.com. Most of these messages were from 58341 but there was atleast one each from 6462883718 and 9177251026. Web searches revealed that these were known spammers. Obviously, the next step was to figure out how to prevent the spammers from costing me $.20 for each spam message that they send me.

A few more searches and an article from NYT dating back to Jun 2008 came up as "the" way to prevent SMS spam. So I followed the instructions and set up my ATT account to prevent spam messages. Only that the ATT instructions seem to apply only to email-to-SMS spammers. From the spam that I received, I can't tell if there is actually an email address associated with the message. In my subsequent tests, I verified that nothing that I did on mymessages.wireless.att.com website actually prevented SMS messages from coming to my phone. (This web-site wasn't particularly easy to use and there is no obvious link to it from the main ATT wireless portal at wireless.att.com.)

As a last resort, I logged into wireless.att.com to turn off SMS completely - even though I would like to use SMS from time to time. Much to my surprise, I found out that there is no obvious way to do this online either - all that I can do is to call into ATT to get SMS turned off by a human customer service rep.

Clearly SMS spam fighting hasn't kept up with the rising use of SMS for spam. Is ATT (and its competition) obligated to provide spam fighting tools? It costs me money to receive all these unsolicited messages, but because ATT actually profits from the spammer's behavior, it is hardly in their (short-term) interest to provide an easy to use solution.

So I am left with the annoying choice of continuing to pay $.20 per spam SMS or waiting on the phone with ATT customer service to turn off SMS completely. Neither solution is satisfactory.