I have gotten the same phone call twice as well, these people just do not give up.
First of all the irs does not make phone calls, to personal homes , they contact you through letters, they do not even ask for anyone, they just say the irs is filing a lawsuit against you, , if they can not get you to respond this way, they try another way, which they already did last week,
Two calls today alone. I call the number back and asked why they keep calling my number. They immediately hung up. I have now blocked the number. Why be on a registry when it does not work?