Yes, if you want to change the ATM PIN then you can do it using the ATM outlet but if you have forgotten it then you need to generate it again. And if you want to generate the new ATM Debit Card PIN using ATM then you must have a one-time password PIN sent by HDFC Bank (either in a welcome kit or sent by SMS). Then after you can follow the above-mentioned steps to reset your HDFC Bank Debit Card PIN using ATM.