Here is what some one said about vsnl tata indicom :

Tata Indicom(VSNL) is one of the worst ISPs in India. The customer service is beyond apallable. They have a 24hour customer service just for namesake but nothing ever gets done.
I have a 512kbps connection from VSNL which has a limit of 1 GB. For the past 2 months I have faced abnormal usage on my account. The usage occured EVEN THOUGH MY MODEM WAS SWITCHED OFF !
After innumerable complaints, the matter is still not fixed. Morever, they have charged me more than Rs. 3000 for 2 months, even though I have used far less than the 1 GB limit.
I think there is a serious security problem with router connections. I found this out recently. VSNL calculates your bandwidth used by your IP Address. They DO NOT verify your username or password when you connect to the Internet. Therefore, it is as simple as changing your routerís public IP Address to someone elseís, and voila it works.
The technical competence of the VSNL staff is really abysmal and I would warn all existing customers to be aware of this issue. Anyone could use your account without having to do much.