Charges on ATM transaction
There is no limit on the number of transactions you can do in a month on both IDFC Bank and other bank domestic ATM networks, as long as you have a average monthly balance of Rs. 25,000. If you don't, then there is a nominal charge in the interest of fairness (to cover our costs of service!) after 5 free transactions a month.
Most people do not need to use an ATM more than once a week, so you should be able to avoid charges completely, even if you don't maintain the balance.