Here's what i've done in the past and it has been successful MOST of the time. Talk to them, get them to send you something in order to find out who they are representing. You will never be able to take action against these people directly so you have to find out who they are working for. Once you find that out, you file small claims suit against the company they are working for and seek damages as permitted under either the state stautes or federal law. Once they receive the complaint in the mail from the Court, they will be more than glad to pay you and leave you alone. I've done it and it works.
Caller ID shows INSACCOUNT. They call constantly. Received 6 calls from them within 1 hr this morning. They say press 1 to talk to someone and 2 to be removed. The pressing 2 to be removed does not work and pressing 1 and asking to be removed results in a hangup from a rude person who will not give their name or anything about the company.