BSNL allows users to change broadband tariff plan through their online portal. If you are Chennai BSNL users then you can use http://www.chennai.bsnl.co.in/ to change your broadband tariff.
In the BSNL Customer Care Portal, navigate to BSNL Broadband services and click the Change Broadband Tariff plan link.
To get the existing details, enter your Telephone Number and Consumer Number and click the Get Details button.
This would display the Customer Service Request page where you need to select the Service Requested as Change Broadband Tariff Plan and the click the Next button.
In the More Details page. select the Tariff plan to which you want to change and click the Finish button.
This would display the following confirmation message about your change of Broadband Tariff plan with the registration details.