Fraud while converting Airtel postpaid to prepaid

I have submitted the request for converting Airtel postpaid number 9920189310 to prepaid since last 5 days.
They have given me new SIM for prepaid which is not activated since Saturday.
Every time I go to there gallery they ask me to come up again and again and provide no satisfactory reason for not activating the SIM neither another solution.
Kindly help.

Thanks
Dipti
9819088897