Because they identify themselves when they leave me voicemail. It's Hollander Law Offices. I did a little research and it wasn't too hard to find their mailing address.
The only place I see them on my report is in an inquiry they made, but I think they're representing USAA, a company I had a credit card through a while back.
All the time...
I don't usually answer calls that I don't know the numbers too, but one time I did answer, and it was during a meeting at work. It was these folks from this same law office, and they said it was in regard to a delinquent CC account. It was either for Discover or USAA, I can't remember which. I ended the call there and haven't spoken with them since.
Thanks for any help/advice you can offer.