Warid increases the Balance Inquiry Charges - June 2013

Warid Pakistan has increased the balance inquiry charges for all of its prepaid customers. The new increased balance inquiry charges are applicable from 22 June, 2013.

I didn't understand the purpose of balance inquiry charges, it is the right of every mobile phone user to know the balance of its mobile account without any cost.

Warid website displays the following message:

Dear Customer, Balance Inquiry will be charged Rs.0.20 + tax per request from 22nd June, 2013

Balance inquiry charges may makes some sense during Roaming or on Roaming networks but Balance inquiry should be free on home network because it is the basic right of mobile phone users.

Can anyone of you tell me the purpose of balance inquiry charges ?