Warranty Services Call and do not place me on do not call list after several requests. Chicago Illinois

I get phone calls from warranty services couple of times a week on my land line and on my work blackberry.

It is generally pre recorded message and if you press 1 to talk to someone. I have always ended up with a representative who hangs up a call on me.

1) I dont want to purchase warranty - not sure why they are calling me even if I am on do not call list.

2) Not sure how they got my number.

When I ask all good questions to representative they hang up getting annoyed.

I tried reaching their corporate office but no help. I googled about this and found lots of customers complaining about such phone calls. I somehow don't get it - how they are trying to do business by annoying their prospects. Unless there is something really strange going on. May be company is paid by number of calls they make/prospects they speak to and this is just a way to make money by annoying people.

I am not able to figure out any other possibility here on what is their motivation.