Mahindra Finance — not getting back my vehicle keys after completing the loan

Address: Kamrup Metropolitan, Assam, 781022

I took loan for my eon sports car from mahindra finance and i had submitted my car keys and 3 security cheques for it to guwahati branch assam on 9th april 2014. I had collected noc from mahindra finance on 27th jan 2018. But the employee name sh. Sandeep said that there office had been shifted so i will get my keys and cheque after few days. Now when i asked for it they said they have not had my keys only cheques they can give. I want my keys back or else i will take some other steps. My vehicle no. As01 bk 6006 & my name is bitopi phukon, mobile no. [protected]