I bought, not one, but two prepaid sim cards, one for my wife and myself as we both had separate trips to Europe at the same time, so that we could at least text each other. And to our utter shock we found out that both the sims did not work at all. I had done all their activation and even called them to make sure that the International roaming would work. But upon arrival in the respective European airports, we both found out that Vodafone are absolute cheaters.
We had used BSNL and airtel earlier, which were fine. It is a pity BSNL stopped the International roaming services on their prepaid cards.