Atm Paid less amount

Sir,
I withdraw cash of rs 15000 from an atm of the same bank in which i had my account, but the atm machine delivers me only 14500 rs i received 500 rs less, when asked to the bank regarding this they told me to give complaint in writing, after 15 days the manager told me that their counting is correct and the atm machine had not done any mistake, please guide me what to do…