They'll call if they know they're going to get any kind of answer. You want to anger them, try letting your phone ring with NO answer at all if you're able. Without a chance to maybe scare you into paying something you don't owe, they'll get tired of wasting time calling you. If you're able to completely ignore unknown calls, your situation will improve.
I got a call from this man in April 2016, and again today at 1:15 PM. I let it go to VM both times. A man with a heavy accent claiming to be "Kevin Mason" left message that is partly unintelligible with sometimes nonsensical remarks about owing money to the US Treasury Dept. for taxes. The number is even from the Washington D.C. area. He pressured a call back by making threats to instill fear such as stating that ignoring the call is a federal offense & there will be serious consequences if I do not call back. It's an obvious scam. I made an audio recording of the message to keep, and then reported the call to the US Treasury Dept. on their scam form here: https://www.treasury.gov/tigta/contact_report_scam.shtml. I told them that I can provide the audio file. Please report this scam.
They'll call if they know they're going to get any kind of answer. You want to anger them, try letting your phone ring with NO answer at all if you're able. Without a chance to maybe scare you into paying something you don't owe, they'll get tired of wasting time calling you. If you're able to completely ignore unknown calls, your situation will improve.