Well, some of them above have explained it well. We need talktime to make certain calls, and also to make use of VAS provided by the mobile operator.
But, i also noticed that the airtel is no more providing recharges for 2 days or so, which was available before. Now, a customer has to make a minimum recharge for 24 days to get any subscribed plan from Airtel. Did anyone notice when the 19 rupees plan which provided 2 days of unlimited calls vanish away?