One should remain cautious about these kind of things. Recently Some one from Vodafone called me on my Vodafone number to verify my date of birth. My reply to him was " How the hell I know that you are calling from Vodafone and why should I give my date of birth to you ? "In reply he told me that " Thankyou for your doubt and concern. I will tell you your address to verify the same. "Then I asked him for my last payment date and amount too. He answered it correctly. Then I told him to ask whatever he wish to know. He asked for my date of Birth. I told him and he thanked and cut the phone.Regarding Documents handover, it looks something fishy.