ICICI Bank Credit Card — Excess charging of interest

The initial outstanding in the month of February'2010 was Rs. 28511.34,
Last date of payment was 25/02/2010. payment was made by 15th. of Feb'10 & the amount was Rs.25000. Balance outstanding was Rs.3511.34.therefore late payment fees may be charged on the balance amount,but inthis case the bank is charging the interest on initial outstanding amount of Rs.28511.34. this is my objection