Not sure in what way you mean pioneering but it was definitely not the cheapest! Everything cost money. Text messages, phone calls, data, roaming between states, out-of-state phone calls. Everything. All this in addition to the cost of the cell phone itself - no bundled offers with phone like AT&T did with Apple in the US.
Furthermore, you could get away with a connection from private companies like Airtel and Vodafone if you lived in a big city. Rural coverage by these players was notoriously bad. The only substitute available was the one provided by the government itself - BSNL - which got a reputation of having the "best coverage".
All that changed dramatically when Reliance came up with a Rs.500 phone which included a connection with free unlimited calls between two Reliance phones. That was the beginning of true mass adoption of cell phones in India.
> People created the 0 cost phone call - farmers and mobile users could give a missed call to a number they heard on the radio, and then they would get a call back.
This is not an example of a model working well. This is an example of a workaround to mitigate high call costs.