Indian Army — about a phone purchased from olc

I recently saw an ad in olx. The seller named wa vikas patel. He asked me to pay for that phone.in adance by paytm. I paid advance as he asked for 4000. I paid that. And he said that i have to pay reat of the money then i could get that phone in my hand. The remaining amount was 8000 ad then the courier boy who have the phone said that i have to pay 4150 for security purpose. If i had any issues regarding the phone my money will be refunded. And till now i haven't got my money. He said he is from army and for identity he gave his aadhar card and gave his canteen card and driving liscence. So unfortunately trusted for that and i got to a big problem. Help me out from this critical situation.
His phn number-[protected]
His bank account details - ac..[protected]
Ifsc. Abpb0000002
So help me out to get my money back