The process would be the following

• Register with your mobile vendor(one time).
• Login to the portal.
• Select Online Recharge / Topup / Flexi
• Enter the amount and sumbit
• Select your bank
• You would be directed to your net banking website
• Login there with your net banking username and password
• Confirm the transfer and submit
• If your transfer was successful you would be redirected to your mobile vendor website showing a success page

Below given are screenshot of recharge of  BSNL mobile through SBI internet banking.

BSNL  login page

Select Top Up your mobile

Enter mobile number and select the denomination

Select the preferred bank

Login to the net banking portal

Select the account and confirm

Confirm the payment again

If its success this page would appear

In 5 seconds it would be directed to bsnl website where there also you can see the succes message if everything went fine

Summary of transactions