Airtel — case of fraudster

A guy from myntra called up at 13:36 on 10/10/17 saying that i have won a lucky draw which includes some expensive gifts. To avail this he asked me to purchase worth rs 4000 or above. At 18:44 another no rang up he asked the card details including the otp no. Falling in the trap i disclosed the otp no and he has debited an amount of rs 20000 at airtel money.
The details are
Tran date debit particulars
10/10/[protected] prcr/[protected]/[protected]airtel
10/10/2017 1000 prcr/[protected]/[protected]airtel
Shreya