I also used tata docomo
The tata docomo operator provide the high data in low cost
I used the operated when it was launch and the network is shared by the Vodafone telecom towers
In past days docomo provide the 500 mb 2g data in 15 rupees coupon and the speed is always good the speed is minimum 20 to 50 kbps
Which is good for the price tag of the data
The network was good because it is provided by the tower of vodaphone the vodaphone also takes the shares of the tata docomo
But after the vodaphone company discontinue to give the network signal the docomo comes bad in the tag of network and the internet speed
I would recommend to use this operater