the cheapest STD call in india

Tata DOCOMO
The best offer i got from net is from DOCOMO.
Tata DOCOMO Tariff Plan
for Rs 24/- STD at 1p/6sec with validity of 30 days.

AirTel
I am using AirTel - it doesn't have any offer.
Maximum they can offer is 1/- for 3min STD call.

Idea
Idea is almost similar to AirTel,,, no offers at all.
Idea Prepaid Tariff Plan
The best they have for STD call is charge for 61/- and get 140min free. :-(

Vodaphone
Worst plan i ever see,,, 
there is no difference to STD calls to same/other network.
Vodafone Tariff Plan