I just got this call - I didn't answer but they left a voicemail. The IRS is about to file a lawsuit against me... I need to call them right away! What a scam! The IRS doesn't call cell phones threatening lawsuits. Impersonating the IRS ought to be a federal crime.
It is, unfortunately the callers are located in India and Pakistan and there's nothing that can be done about it at the present time, although US based money mules are arrested now and then. Invest in a call blocker and DO NOT pick up on call numbers you do not recognize.