I have no clue who these people are, but I just called their number to be removed from their list. The automated response said it would take 20 days to be completely removed.
Keep your landline. I purchased a call blocker box on ebay for about $50(use "caller id block" as your keyword search). These jerks have been pestering me for six months until I plugged in the box. I finally have peace and quiet and this only works on a landline (in the US). No more pointless calls from idiots.
Talking to these people doesn't help, they only hang up on you or swear at you. They use an autodialer to dial random numbers, so there is no "list" to be removed from.
Just got a new house and had Comcast do the cable/internet/phone. Within a day of installing, these idiots call at least once a day - for about 2 weeks or so now. At least on week days, no one is at home because we both work, but on weekends it gets annoying. Signed up for the do-not-call list, but still have to wait until around mid-Feb. for the 30 days to kick in. As soon as it does, I will make sure to let them know. Thanks to everyone posting - it helps a lot. Anyone have any good solutions to have them stop calling?