I worked in a call center the summer in between high school and college, and the company I worked at was very cognizant of the various laws. This was before the federal no-call list was enacted, but I'm positive they strive for compliance with that as well. If people asked to be taken off the calling list, we had to flag their call as such and if we were caught not doing that, we'd get in trouble. Their were nuances to it though. You had to specifically ask to be taken off the list in order to be scrubbed entirely. If you said "no thank you" and hung up, you were getting called in 24-48 hours without a doubt. If you gave two "no's", you were scrubbed from the campaign, but not the global list.
It was still a terrible and shitty job, but it paid a few bucks better than minimum wage and the company was fairly lax on attendance (I was 17, so I had different priorities and a general lack of responsibility).
The worst day of my two or three months at that job was when I got put on a calling campaign for some mega-church. I felt terrible asking people who probably didn't have the money to donate to give up their money to this organization that was clearly raking in tens of millions a year and whose leader/minister/whatever was a multi-millionaire. Thankfully, I only had to do that one day and had so much motivation not to take in a single dollar, that I failed to land a single donation and was moved the next day to trying to get people to do balance transfers on their credit cards. Still annoying, but at least I didn't feel like I was robbing people by appealing to their faith and handing their money over to some evil creep.