regarding illegal cash withdrawal from my savings account

dear Sir,
in July 2017, I visited bank to withdraw money . as each time , I deposited one filled up withdrawal slip with putting two signatures on, with passbook at cashier counter. after sometime cashier and peon told that my withdrawal slip had lost. then they said to fill up other withdrawal slip and to submit at counter but I denied to do so. again they said if he got lost withdrawal slip he would tear it so I submitted again. but next day I went to bank to update passbook and got shocked both withdrawals had been transacted. thereafter I complained to branch manager next regional manager also zonal manager . after five months I got reply letter from regional office mentioning both withdrawals done by me. I also complained banking ombudsman but they replied me in written that this complaint is out of my consideration and closed this under 13(d) rule. I also complained consumer forum but haven't got any satisfactorily reply . when I got reply letter from regional office confirming two withdrawals by me then I requested to copy of CCTV footage. after four months it was provided and saw only one withdrawal and reported to branch manager from where I got copy of the CCTV footage then they said me to ask regional manager how they proved two withdrawals. then I visited regional office again and took complaint again from my side to verify again.
but I think regional office won't take any action against branch.
then what should I do? I have only one point that is CCTV footage it can't prove two withdrawals.
it's a very complex matter but money is not small it is matter of 20000/-. how can I left.
should I lodge an FIR but on what basis?

please advise me your precious suggestion in this regard to take action against bank.
thanks.