Union Bank Of India — non refund of money wrongly debited

My union bank savings account no. is [protected]. I tried to withdraw Rs.2500 from my bank account in Union Bank of india via my debit card on 3rd Oct 2018 which had failed. Although money was debited from my bank account. I called the customer care number immediately. They asked me to wait for next 24 hours and then register a complaint if the money does not get credited back. Next day i.e on 4th Oct 2018 I lodged a complaint via complaint no.[protected] . They asked me to wait for the next 7 working days to get the money back. I did so. But today i.e on 15th Oct 2018 after the expiry of 8 working days, when I checked my bank account balance, the money had not credited back. So I called them back But when I called the same customer helpline no., no one answered my call and my call was kept on hold for a continuous period of more than an hour. I don't understand why it is taking so long to refund my money.