Enter the following codes as you would dial a phone number into your phone and hit dial, a sms like message will be returned with the requested information free of charge.
Below is the description of each code and the code you should use to retrieve the respective information.
|Balance & Validity||*123#|
|Local/National SMS Balance & Expiration||*123*4#|
|STD Balance & Expiration||*123*6#|
A simple tip to make this easier in the future is to set a contact in your phone for example Airtel and save each of the necessary codes as a phone number like the example screenshot below. So when you need to check a certain balance all you need to do is hit dial on the respective code/number.