Had the same thing happen with a debt collector. They would identify themselves, but seeing as their name was meaningless to me as we had no prior relationship, and even if I knew what they were calling about I had no debt I was aware of...

They were a _little_ more cooperative about it though.

    "Hi this is <Person> from <ABC Inc.>. Can I start by confirming your name and date of birth?"
    "Who is this?"
    "<Person> from <ABC Inc.>. Can I start by confirming your name and date of birth?"
    "No, you may not. What's this regarding?"
    "I can't discuss that with you until you verify your identity."
    "Okay, well I have no idea who you are so I'm not about to do that."
    "Well, I can't tell you anything else until you confirm your identity for me."
    "Okay."
    "So can I get your name and date of birth please?"
    "No."
    "..."
    "..."
    "..."
    "..."
    "Can you tell me what _day_ in January of 1970 were you born?"

I'm sure it broke some rule somewhere, but at least giving me some verification that they already had some of the information they were asking for I was willing to play along.

(Turns out the ISP did their usual ISP thing and failed to mark that I'd returned my modem when cancelling service a few months prior then told no one and sent it to collections. The debt collector was very adamant that I needed to set up a payment because this wasn't going away. I walked into one of the ISP's retail outlets, told them what happened, they sighed heavily because this comes up _constantly_ and called in to have it marked returned and I never heard from anyone ever again. The end.)