Person of indian origin but not a citizen of india - bank a/

Dear Sir

I wish to know about the RBI guidlines for savings bank account status.

If an Indian citizen took a foreigen citizen ship.  He is also holding an OCI/PIO card.  Now he wish to come bank to India and permanently settle in India.  He is operating an NRO savings bank account.  I wish to know that after 6 months he can change his NRO savings account to an ordinary savings account.  Some of the banks informed me that he can do and some others told me that he can't do.

Please let me know the rules