So I've just called Vodafone and asked them about this, mentioning the advice given above from "Kirsty", and the gal said that they "can't just block one number", I tried to explain it to her that lots of people seem to be having this problem etcetctec.... She asked me to repeat the number a few times and then a light went on in her head and she said to just text the word "STOP" to that number and it should stop. It sounded sort of wierd and cryptic, but I'm willing to try anything to stop this, so I've sent the text. It could be a money-making scheme on VFone's part getting you to waste text money, but if it works, who cares!? Give it a try?