This scam claims they are the IRS calling to let you know they have filed a law suit against you and to promptly talk to them. When I called the police department, they told me this is a scam going on all over the US and federal agents are working on it. The IRS NEVER calls you, instead they write you a letter informing you of their questions. Beware as this is a way to steal Social Security Numbers and steal money.
You can do something about it by just letting the calls go completely unanswered. Sooner, or later, they'll get tired of calling numbers that have no answers since they can't make any money off them.