I just got one of these too - and since they called on my home office line, I called back. They were looking for someone else and apologized and said they'd put me on the do no call list - surprisingly enough, they were polite. Don't know why they were calling
I got a recorded phone call saying that they had attempted to call me three times and that I should call them back. I was placed on hold for almost 20 minutes. They claim no one could speak with me and they refused to say exactly who they were and what they wanted.