Airtel — requested for porting from idea to airtel prepaid but ported to airtel postpaid

Address:

560090

My name: amaresh
Number:[protected]
Date of porting: 23 october 2018.
Number activated: 28 october 2018.
Airtel executive: deepak gowda - [protected]
Money transfered for prepaid plan mode is google pay (Screenshot attached)

The airtel executive came to my office for porting my number. Said he is converting my number idea postpaid to airtel prepaid, he gave a new sim saying it is airtel prepaid and will be activated in 5-6 day, and took 200 rupees for prepaid plan.
But now i got the postpaid bill 350 rupees this is horrible a cheat.
I called the same executive and he is saying he is not the airtel executive but a hdfc bank executive.
This is very serious issue, i want this has to be considered seriously as i lost the money and this is fraud from airtel.