Do not respond to unwanted texts or emails from questionable sources. Several mobile service providers (including AT&T) will allow you to report unwanted spam texts by simply forwarding them to 7726 (or “spam”) to enable the providers to prevent future unwanted texts from the specific sender.
TIP:
Put 7726 in your contact list, so you can easily forward those unwanted texts!
For further information and citations, click on the "Info" button, below (Javascript required).
More info:
http://en.wikipedia.org/wiki/Mobile_phone_spam
http://blog.usa.gov/post/89152807112/protect-yourself-from-text-message-spam
However, in many cases, the text origin, as seen on your phone, is faked. The internet domain does not exist, or the phone number may have been spoofed.
Please reply to this post, and let us know if you tried the suggestion, and if it did or did not work.