Pranab bro, here's the procedure
Purchase Apps/Games with Net Banking from Google Play Store
Open Your Play Store
Now Move to that app which you want to buy
Click on the Price button and proceed further.
After accepting terms & conditions, it will show you a screen to choose the payment method.
Now it will show you the following Three Options,
1. Add Credit or Debit Card
2. Add Netbanking
3. Redeem Code
Now Choose NetBanking, and it could ask for billing information so fill it.
And proceed for next,
Now it will Display the list of banks which google is accepting, all major banks of India are listed over here,
you need to choose of which you use Netbanking facility,
Now it will show you the option of BUY, now after clicking on Buy it could ask for the Google Account Password,
Now it will redirect you to Your Bank,
Now enter your banking details like userid and password, then proceed.
After Successful Payment, it will redirect to you Google Play Store Dashboard.
Now it could ask for " How Often would you like to confirm your password for purchases? ” you can either select Every Time or Never, it’s all your choice.
Now after clicking it will show you Payment
Successful, installation in Progress and will give a button to Continue .
Yes, it’s done, you have successfully purchased an app from google play store using your netbanking.