this caller always hangs up. never answers back , and line goes to busy

Calls up to 5 times a day but never anyone on the line when I answer - I tried to call back but only get busy signal

Caller ID: Nat Auto Div
No answer after greeting caller.

Caller said name and co info so fast I didn't understand.  Sounded like he was looking for some type of mileage info??  When I said "I didn't understand a word you just said", he called me ignorant.  I just hung up.  Very rude whoever they were!  I called number back to see who it was and a recording said the number was not valid.

Did not answer.  No message.