HDFC Bank — dispute amount debited from my account and not yet refunded

Address:

W.31 2J/6, Gandhi nagar, L F Road, Cumbum, 625516

On 28/11/19, i have swiped my card in KLM airways Delhi airport for extra baggage (Rs.7150) and extra weight (Rs.7150). total Rs.15020.
The transaction was successful and amount has been debited from my account successfully.
Next on 01/12/19, i have not swiped my card anywhere and i have not used my card. But suddenly i received two messages saying that amount Rs.7510 was debited twice. so total Rs.15020 was debited from my account without any authorization.
I have contacted HDFC customer care for last 2 months, but no proper response and i tried mailing them.
Receiving only acknowledge mail and there is no action taken from their end to refund my amount and there is no proper root cause for the issue is found.