I also faced the same problem with their prepaid connection.
I purchased the Tata Photon+ Prepaid connection on 5th December, Thane Naupada branch billed me for the full amount but gave me inactive SIM saying that currently there is some technical error at the backend and SIM will be activated within 2 hrs!!.
The SIM did not get activated for 3 weeks!! I called there customer care but they had no clue why SIM is not active, everyone gave me all possible reasons like server is down, technical problem, address not yet verified, phone number not verified etc.
Finally I went back to Thane Naupada branch and realised that Tata Photon is supposed to be installed on your Desktop/ Laptop with a username and password which nobody provided at the time of buying nor did anyone at call centre.
Again after using for 5 days my SIM was blocked.
This time again I had to go to there service centre at THANE NAUPADA on 1st Jan 2010. Customer care executives told me we called at your number for verification but you dint pick the call so the SIM is blocked. Again I put an application to unblock it and was told it will be active in 2 hrs. I waited for 2 hrs, 3 hrs 4 hrs... Then I called there call centre they told me it will be active not before Next day 8p.m. that's good 24 hrs.
But hey... It did not even get active till next day 2nd January 8p.m.
Again on 3rd Jan 2010, i went to their centre, this time they said while using the internet your balance went to -ve Rs.3 so we de-activated your number but when I recharged the SIM even then the SIM was not activated. This time they said within "3HOURS" it will get activated. This was at 4.30 p.m. I waited at the centre itself for 3 hours as by now i knew that even after the new 3 hours it will not be activated. and as guessed by 7p.m. they told me technical team at back end is on leave so we will activate it tomorrow.
It is 4th Jan 4 p.m. and the card is still not active.
My money in Tata Photon+ - Rs.3, 500 has been a complete waste!!
Suggest anyone buying the connection to not pay the money till you know the card is active.