Unless I'm mistaken, a BSNL broadband account can be used only via the particular phone line for which it was given. So you cannot use your shop BB account through a different phone line at home.
Answering the last part of your question for the sake of clarification, yes, you can configure a broadband connection so that you can access it, as you said, "dialing by username & password" rather than configuring it as 'always on'. This is a good way to prevent unauthorised use of an account. However, this too can be done only through the phone line for which the BB account is provided.