The information is sold on but im not sure who starts it all off.
If you get a text and it says 'text 'stop' to opt out', don't do anything, just ignore it. If you text back they know the number is live so you go on a list which then gets sold on and it repeats and you'll start getting more.
Same with answering calls you dont know who they are, same applies.
Ill try and find out the numbers you forward them too, I had them ages ago. Its different for each provider