Airtel: potential tapping and abuse of personal information??!

A couple of days ago, I had a conversation with one of my relatives about a College that provides Management courses. Yesterday I got a Advertisement message about the same college that reads:

AD-

@place offers UG, PG courses in part-time and correspondence at Affordable fee. For more details call email:

What is puzzling and annoying to me is:

• How did I suddenly get an message about the college I was talking about over phone suddenly?
  
• How come I got the message just a day after I had the conversation?
• Why do the 'Don't disturb' that I'm enabling every time whenever I received unwanted messages, never seem to be activated?

While whether the information was useful to me is secondary, it is not clear how they could get information that they think could be useful to me? Where is Privacy?

Is Airtel tapping calls (automatically/manually) and helps spammers?
If this is the case then Airtel should be held accountable for Tapping, Misuse and abuse of personal information and snopping on people. An, usually happy Airtel customer for years, I'm finding this hard to believe.

Has anyone experienced such instances before?

Note:
1. I have never heard or mentioned about the college prior to that conversation and it has no relevance to my current profession.
2. I never used to leave my phone number with websites.
3. Please feel free to pass on this information to make people aware of such abuses.

Ps. I could register a complaint with Airtel, but they could easily give excuses and might claim that this is just coincidental.