Owner is not refunding the lease security amount after completion of period

I have taken a 2 BHK apartment in Bangalore by depositing 12 lakhs of rupees as a lease amount for a period of 3 years. As per the agreement, the owner will refund back the total amount of 12 lakhs after completion of 3 years of period. The agreement was signed between me (tenant) and the owner with two witness. I have informed owner through e-mail for refunding my security (lease) amount as per our agreement but they are not returning my security amount. The key of the apartment is with me but presently we are not staying, only visiting occasionally. I have requested the owner several times through telephone and what's app but not received my money back. For last one year I am following them but every-time they have informed that they are trying. Please suggest me what to do now in this situation. Please note that I am a retired govt. employee and the above money was given from my retirement fund only. Presently, I am not staying at Bangalore. Kindly suggest what to do now. Thanks & Regards, Pradip