Airtel — postpaid to prepaid conversion for [protected]

I wanted to convert my postpaid sim into prepaid and i submitted my request with all documents at airtel store in samalkha haryana on 30/08/2017. They took 250 rupees from me telling it my postpaid bill and additional 130 rupees for the new prepaid sim. Till now my request has not been forwarded by them nor the 250 rupees been credited to my bill. Again they callled me on 08/09/2017 and told me to credit extra rs.50 as my pending postpaid bill. Moreover they are not issuing any form of bill for the payments made by me towards them of rs.250 and 130. They are just maintaing a manual register for the payments and i doubt if they had made that entry for my bills in that register also. Please look into the matter as its the case of harrassing a customer and extortion o[censored]ndue money for him.