How can i get rid of cold callers?? i do not want a conservatory!?

about 6 or 7 times a day i get calls from all sorts of different companies, trying to get me to change my phone call provider, buy a mobile phone, get a conservatory on my house or buy a time share. i am getting sooooo fed up of them i just want them to stop. i remember watching richard and judy once and they had a few great websites where if you put in your details it will stop all these calls. does anyone have any information on this at all??