Wishbone: but an actual telephone number has to be managed by an actual phone company, and they have to know whose number it is.
real.geizterfahr: Not necessarily if it is a prepaid mobile phone. Here in Spain you could buy prepaid numbers without identifying yourself, until a few years ago. I think it was in 2009 when I had to go to a shop to give my personal information, to keep the number. And when this was possible in Spain (a member of the heavily regulated European Union!) a few years ago... Who knows what's possible in India.
Oh, I just seemed to remember from the spam that it said it was a UK number. I may be mistaken. And of course, you may be able to buy a number in the UK without giving any information, I don't know.