Don't know about GPRS being charged OR not as I'm not an AirTel user so I'll answer the other query.
The bad news about this Sire is either you have a very efficient rootkit http://en.wikipedia.org/wiki/Rootkit infiltrating your system OR a better outlook is a lot of background applications are running, these can be switched off by going into Run --> msconfig,go into Services and check what all are running in the background and kill them [the ones that you do not require].
Please post your system configuration and OS for further help. Cheers!!