What's my number?

Not too long ago, the cover story of one of the weekly magazines proclaimed we have no privacy. Our personal information is being sold to parties with diverse interests, cheaply.
While the article dismayed me, I was more or less certain that no one except my family and people i know has my number.
Yeah there was the odd fone call from credit card companies asking me if i wanted to get a card, but never often. This morning though, i was in for a shock.
First i get a mail on gmail from a study abroad consultancy, asking me to make use of their services in my search for good courses abroad. I had been told of google's search funda and how gmail sends ads which are most relevant to me. I am impressed.
I write back, volunteering no details on myself, but seeking information. An hour later, i get a call on my cell. From the very same consultancy. Though i was impressed at their speed of getting to me, I had to know how they got my cell number!
On prodding I heard they hire a 'PR' agency which gets them databases. Where from? 'Probably airtel, I dont know.'
Id like to file a case against airtel for leaking private information- for not ensuring safety of my information and letting callous employees sell them for a price; or worse, selling it knowingly, i said to my friend. I recounted cases of the people who were out of town on roaming, forced to pay the surcharge on the call they picked up that was a direct marketing call center executive.(they always end up wasting some more talktime in screaming at the them for wasting talk time)
My friend said, I must empathise with the sales people. Afterall, how else will they get to me? And if everyone were to object to their calling up, what happens to all the day call centers calling up for selling products?
They do hear a lot of rudeness thanks to their invasion of our privacy. Cut throat competition will ensure that if one firm doesnt, another firm will get to me, thru these very means. And maybe get my business too. I am really curious though, how much increase in sales do they see through such means. Does it even help really?
Would passing a law (i believe such a law is in the offing) stop it?
Do free market advocates agree? (I ask this because of an interesting rhetoric on why patents and copyrights ought to be abandoned.Unrelated I know but propelled me to wonder what might be said on the issue of invasion of privacy. Does it fall into a similar domain?)