I keep getting these calls and no one answers, I most likely will call my provider so they can block the number. I have tried this before with another number, and I have not received another call from a previous number.
received call at 12:38pm 1/18/12 to a recorded message from EFA Survey Group. Listened and pressed 9, receiving "confirmation" that my number had been "permanently removed" from their list. We'll see. I have added "DO NOT ANSWER" as the contact name for this phone number and set the default ringer to silent so that I will not be annoyed again. I can't find any record of a company with this name on the internet and with so many posts from unlisted cell numbers I am sure it is a scam. I hope that's all that happens.
These people change numbers so often that it's impossible to keep them on my "reject" list, and they don't dare show their name on Caller ID (This time it just said, "Texas"). The fact that they do this is enough to tell me that they are bottom-feeders. 'Nuff said!