BSNL (Bharat Sanchar Nigam Limited) will be a very familiar name for Indians. It is the largest communication provider in India. If you are a BSNL customer here is the official applications for the smart phones which you can use to know about your service details and also to make payments.
These applications allows you to
Bill Payments via Credit Card, Debit Card or Internet Banking (Prepaid, Postpaid, Broadband, GSM, WiMax, CDMA, etc.)
Know prepaid balance and validity
You can set a mobile number and email address to get payment information via SMS and Email.
Android application – link
iOS Application – link
Requires iOS 7 or higher.
Compatible with iPhone, iPad and iPod touch
Windows Phone link