Ah, thankfully most days I am out so never actually experience these. Today however I did get quite a plethora of these calls. Like many, left BT, and suspect that this is why 2Touch are calling me, because of my former affiliation with BT. I did however phone up their switchboard +44 (0)191 525 7000 and politely asked to have my number removed from their database. The woman was very polite and said that it will be removed from their dialler, but may take a couple of hours to complete.
Having lived in the US for a year, I've learnt to screen my calls at ALL times, sorry family and friends, but you might be trying to sell me crap (actually, sometimes even they are ;-)