Phone rang, got a busy signal when I answered.

I have a car for sale online. When I answer I get total silence. I have also gotten many calls from unknown numbers since posting my car online.

Its a scam... you're selling a car... they call and try to get you to sign up for a few hundred dollars... you'll get no results.  SCAM!!!

I think they're called Expert Auto... from Vegas

Don't Answer. Don't Call Back

They use a fake local number... they're doing this so you answer, and so you can't look them up online because they have a number from every area code set up in their dialers.