Mobilink indigo cuts its tariff by 50%

Mobilink Indigo will cut its call rates by 50 %t on all packages from 11th June 2010 to 11th July 2010 for all calls made from 6 PM to 3 AM.
This discount will be available for only on-net calls.
How to Get this benifit?
Indigo customers can avail this offer by dialing 111.
Charges
One-time subscription charges for this offer are Rs. 100