Called left a voice message that cut off beginning to identify who they were but asked to call back. First call back several rings and then busy tone (I expected that if this were IRS, I would have immediately heard you reached IRS). Second call attempt, Indian person said is name was agent Dave (something).  IRS agents NEVER give first name.  Next he asked for me to confirm last for oz SSN and birthday.  I made something up.  He then asked me to get a pen to right down case number.  I "air wrote" it. He then insisted and demanded I repeat this crazy long case number back.  I refused and hung up