Selling between Exchanges

They say if you have bought share in NSE you cannot sell it on BSE.

This is partially true.

If you have bought share on NSE you cannot sell that share on BSE on the same day.

If you have the delivery you can sell it wherever you want. There is no extra charge for this.

So if you are selling the delivery sell on that exchange on which the rate is higher. You will easily get 10-15 paisa difference between NSE and BSE prices.