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

As soon as the status gets changed to RNOR (depends upon your stay in India in that particular financial year), it can be changed to normal savings account.

There is no such time limit of 6 months. 

The regulatory requirement is this - if a person becomes a resident as per FEMA, he has to re-designate his non-resident accounts to resident accounts within a reasonable time post return. What is the meaning of "reasonable time" has not been defined in FEMA. 

If your friend is returning permently, he will qualify as a resident from the day he lands in India & should get his account redesignated within 2-3 months. 

Bank is wrong if it says it cannot be done. Also, some banks follow unscruplous practice of asking returning NRIs to close non--resident accounts and open fresh account (this is done to help them meet their targets)

In case issues persist, file a formal complaint to greivance redressal department on bank's website.