excess tds

my client has taken a unsecure loan from a company @ 9%.he had paid interest @ 9% every year.

but in 07-08 he wrongly calculate Interest @ 15% and deduct TDS accordingly and TDS Return submitted.

now he came to know that excess interest  is being charged.he has rectified entry for interest in books of accounts.now he want to file revised return and claim refund for excess TDS deposited.

can he do so?

is there is any other way to overcome above problem