I am using BSNL 500 COMBO PLAN BROADBAND connection and have visited bad sites.Will bsnl hav histry of sites.I have deleted browser history???moreover I have typed directly the **** address.The usage details in bsnl site is not updated.Is there any probs.

Nothing to Worry!!!
BSNL sometime takes months to update Broadband Service Account.
Yes, They have your Records but don't worry they will not do anything

Dont worry dude, you are not only the singly person who visits these sites. Why you worried about BSNL? Here some tips to reduce your broadband bill,as you are using limited data plan
http://www.techlineinfo.com/ten-tips-to-reduce-excessive-broadband-bill/

You have grownup and nearly 18. Dont worry about visiting bad sites. BSNL dont keep your browsing history and your daddy dosent get a bill with details of visited sites. But if you commit any cyber crimes from your pc they have their own methods to find it. So frequently visit sites like wikepedia and visit Good "bad-sites" less times.

yo BSNl don't giv a shit abt what sites u visit so chill out man.
if not now then when r u goin to c all this.stop worrying n enjoy.
be sure u use it only during 2-8 as ur usage amount may take a max