Collection agent for a medical bill my elderly mother incurred.  She has no money and cannot pay the bill.  He was Very, Very nasty.  When he got really obnoxious I hung up.
George

Got a message on answering machine with a man's voice, saying this is a private call intended for David only. "Please call this number. This is about a debt that needs to be collected. Please reference number ##### when you call back, This is very important."

This is a credit collector looking to collect a debt

This person has called my mother twice and asking to speak to her sister.    My mother stated the person he is asking for is not there he then asked for another person and my mother said not here.   He was very sarcastic to my mother and pushy.    He would not identify himself nor the Company he worked for.   He called about one month later and this time just as sarcastic and pushing my mother for information.    She indicated she was going to call the Police and he said he will call her back again in one month.     In looking back on the caller ID for the phone number this person's name appears to be Carl Ross or Karl Ross.   If he should call you be cautious and best to call your telephone company and try to have the number blocked.

Unsure who this person is.  He was rather rude so I was rude also.
When I called him back he advised me to not call this number again.

The gentleman who called was very sarcastic.  Advising he was given this number by a family member... which is a lie due to the family member is in a nursing home and has Alzheimer's.  She would be unable to give this number.
I am not sure if this is a scam or a legitimate claim.