Tata DoCoMo is the cheapest mobile operator in India.
DoCoMo is very popular for their cheapest plans. I am using DoCoMo from 1 year.
The experience with DoCoMo is good but not great. They provide many offers to their customers which is a very good thing. The call rate of DoCoMo is also very less than other operators.
The biggest issue of DoCoMo is their network coverage. In my area signals are good but the network is not stable. Sometimes there is only one signal in my mobile. They should have to improve their network coverage. I am using their 3G service and the speed of internet is very good day and night but 2g speed is worst. Call quality is good and there is no disconnection while calling. Customer support is also good and we can chat with them online. I would definitely suggest to go with DoCoMo if u have good signals in ur area.