Do not answer these calls, once you do you will continue to get calls from all kinds of unknowns. Some calls are placed to varify active numbers and your number gets placed on a phone list that is sold to these people. Ignore them, they are no one important to you. Don't let yourself be used as a means to make someone money.
So, how much did it cost you to get that advice? Did you lawyer tell you that you need to know who is calling and where they are located in order to serve them with the complaint?