Never vote for anything by sending a text message. Apparently that gives them permission to sell your cell phone number to spammers. I think it was the Pepsi Vote people who did it to me, because they're the first place in almost a year I text-voted at and this and a dozen other started flooding my phone after.
The spam text message I received was:
"As a Thank you for visiting our site, we are giving our customers Gift cards! To claim yours, use code: csv1000
Visit: GIFTCARD2.com
2end reply stop"
If you actually go to giftcard2.com it redirects to http://track.brandnewprizes.com/SplashPage.as ... giftcard2&se=04 which is an obvious scam site. To get the gift card, which you may or may not ever even receive (not sure; didn't sign up to find out), you have to first complete at least one survey, 2nd accept at least 2 sponsor offers where you have to pay for junk you don't want and agree to let them spam you, and 3rd accept that the gift card company is allowed to spam you in the future and sell your number to anyone else they want to.
Best thing is not to reply (their opt out really is just a way to confirm you're a live person so they can sell your number to more spammers) and, if you keep getting spams, change your cell phone number, since, unfortunately, FCC doesn't regulate texts even if you're on the DNC list.