you need to open a new NRE/NRO account with relevant KYC na documents. more
In my experience ICICI is one of the best bank to provide good services to NRI as well as corporate banking segment customer through their huge branches and dedicated channel employee and customer care more
However with my own experience, I would suggest ICICI.
For Mr Khan, none in particular, except that you need to notify the bank first. I do not thing the account can be converted just like that. You need to open new NRE/NRO accounts. more