After having a quick chat with Brian Wernham (@BrianUkulele) on twitter about Spam Text Messages, he mentioned he replied with STOP and it hasn’t helped. I replied saying that IMHO that if you reply STOP then they know they have an active number and will more than likely sell it on.
So rather than reply stop forward the message to your mobile operator:
Orange, O2, T-Mobile and Three: Forward the SMS to 7726 (SPAM)
Vodafone: Forward the SMS to VSPAM (87726)
This can only help stop the unwanted messages. More information can be found at: http://www.tpsonline.org.uk/tps/mobile/unsolicitedtextmessages.html