If you are on the DNC list and ever request information, that request allows you to be contacted by anyone, unless you re-register with DNC.
When in college one of my sons took a telemarketing job. They were not allowed to disconnect the call, if the person they were talking to said they weren't able to contribute to the cause they had to go to the script for the next response, etc. Only the person that they called could disconnect -at the place he worked, if they disconnected they would be fired, they also would be fired if they didn't meet their quota. He quit after 2 weeks as it bothered him that he would get elderly people on fixed incomes and when they would say they couldn't afford it he couldn't just move on, and many times they wouldn't want to be impolite so they would just keep saying they couldn't do it and he had to reply with another script.
What I do, if I get the recording for something more than once I hit the button to get a rep. and when they come on to "make the sale" I just ask them to take me off the calling list. If you expect they may not or that they may call you again you can make note of the company name and the date you request to be taken off. If they do call again you can report them with the date you asked to be taken off and when they called again.
Maybe the best thing to do is to register on the DNC every week then maybe you will stay current with not being called.