Airtel — Change of postpaid sim to prepaid

Address:

East Champaran, Bihar, 845401

I had applied for a transfer of sim from postpaid to prepaid convertion and as the sim is from west bangal and it is to be converted to prepaid sim of bihar. So we submitted all the related documents which was asked from us but even after a month no action pp pm pq is taken and response is given to us. They even charge us 50 rs for sim convertuon which i think is not required.
Kindly response the request as soon as possible.