In the USofA, telemarketers are required to maintain their own do not call list in addition to the national one.
Therefore, you can do the following:
1) insist that you get the name of the company as well as the name of the person and their manager.
2) then say the magic words: "Put me on your do not call list."
3) hang up.
Keep a log of this information: who called, time of call. The log becomes your primary evidence in pursuit of damages.
If a second call is received from the same marketer, regardless of the reason for the call (i.e. if it is for any other purpose or a different client), you can use the log information to sue the company.
This is a federal lawsuit since the rules are federal in origin. Thanks to the ridiculous oversupply of lawyers in this country, one can be had to pursue this for little to no money from you. It should be worth at least $10,000 to you in actual and punitive damages and fines.
Cheers,
PH