They call my office and my bosses office upwards of 5 or six times a day on average, asking for my boss or the head of the IT department, or verifying all of our company information so they can send out us an IT package.  When I told them that they call several times a day and asked to be taken off their list, the person told me that I didn't have the authority and that it needed to come from my boss directly. Then, he hung up on me after a hurried "have nice day".

these people are digging by chipping away.  They appear to be collecting information little by little, then they offer that information up in conversations in hopes of establishing confidence.

My recommendation - take a few minutes out of your day and do as much as you can to waste their time.  Only if you make it in their disinterest to keep you on their calling list do you stand a chance of getting off it.

Called my office line and asked me to confirm information about myself and our company.  Didn't name a company and when I insisted on one, gave the very generic "Customer Advice".  I asked to be taken off their call list.

Cannot believe that I haven't written up this number yet.  Agents usually call several times a day, but it's gotten worse this week (full moon?).  Normally, they claim to represent overnight services, banks, or IT companies.  They want to send white papers, verify our address, or connect their supervisor to someone here without knowing the reason.  So far today, seven different people have requested non-existent Marketing employees; one hung up when I asked the purpose of his inquiry.  A few months ago, a really strange guy was indignant that he couldn't buy a product directly from corporate and had to visit a store.  Maybe this phone is a cover for Skype.