This number is associated with a porn company (http://dsza.com/) who are sending spam text messages to phone users who did not subscribe. Tried ringing this number to stop them spamming my teenage son's phone (his phone has always been blocked from premium sms) but all I got was a voice message asking me to leave my number and they will get back to me. If anyone has any other  suggestions to stop this unsolicited sms, please provide.