Indian Overseas Bank — atm didn't dispense money, but money got deducted from the account

I'm writing this on behalf of my mother.

My mother holds a savings account at iob mysore main branch. Account no - [protected].
She had been to new delhi on 22/04/2018, and went to kotak mahindra bank atm in raj guru road, in order to withdraw rs 10, 000.

But the atm dispensed only rs 2, 500 while rs 10, 000 was wrongly debited from her account.

Transaction date - 22/04/2018
Time - around 9:30 am

So far, the remaining rs 7, 500 has not been credited back to her account, and the bank doesn't seem to have something called as "customer care". The customer care seems to be an alien concept for them.

None of the bank officials we emailed to, bothered to respond.

And find the attached photo of the situation their "standardised public grievances redressal system"