I don't understand why is the "Other" option there. You could've very well listed all the players and kept a last one as Couldn't Care Less.
According to me, its gotta be Airtel. I've been using it since day one when it was introduced in Mumbai, with the pre-paid series 98921.
I'm currently using Airtel's EDGE on a postpaid connection paying Rs. 99 / month for unlimited usage. But you really gotta have "contacts" to get this plan.