You can't TALK if you don't have balance in your phone... agreed !
But why can't I make a CALL despite ZERO Balance??? DON'T let me talk but at least let me ring that number so that he/she might call back!!!
Not every emergency means dial 100! (and u know how responsive they are)
They say, Misfortune never comes alone and 'Murphy's law' says that you run out of balance just before you run into some trouble or have to make an urgent call.
It would be a boon to girls and in the wake of Delhi Gang Rape when the govt is setting up a dedicated helpline 181, I guess "calling without balance" is the least state can do for its citizen, women in particular.
I don't know about the technological details of how it can be done but I know IT CAN BE DONE!
And the economics of this facility is quite lucrative too. cuz eventually, a call is being made from the other end which means revenue. I agree that it directly doesn't benefit "Service provider 1" (cuz the call-back is being made from Service provider 2) but eventually it will all even out in the long run.
Damn, I ran out of balance but I still made a 'call', would you like to "call back" Mr Sibal?