Aircel ISD is cheap compare to Other Operators

Aircel ISD is cheap compare to Other Operators.
You can call
US/CAN (Except Alaska, Hawaii and Guam) : Rs 1.75 per min
Where other operator charges more then Rs. 6.40
UK (Fixed) Rs : 3.75 per min

Why Other operators charge 50 % more form customer for ISD calls ?

Aircel is new service provider in delhi who is planning to launch there service in many circle thats why they are offering such scheme.