Airtel — conversion of airtel postpaid sim to prepaid

Address:

Mumbai City, Maharashtra

I have applied on 7th april 2018 for convert of postpaid to prepaid of my airtel sim. the reference nuber which is given by customer care for complaint is 85291291. till date the matter has not been solved and meanwhile my postpaid bill is generated even not using foa a single call.
airtel has giving frustrating experience.
i really so upset with the airtel service.

i have also submitted relevant document and passport sized photo twice.
i always visit to airtel store, the concern person assured me that the conversion will be done in 2 days.

kindly solve the problem on urgent basis.