Airtel — no service still getting charged

Address:

Pune, Maharashtra, 410014

I have got this my number from airtel 2 months back.. M not getting single sign of network availability still they are giving me one after another bill. So many time i went to their store for cancellation but they are not willing to help.
Everytime they just say, you need to complete 90-120 days. If i getting not any service n you ppl are charging me why the question of minimum days arrive.
I just want them to investigate about it and get my money back for the time i didn't use service.
Name richa mishra
Email [protected]@gmail.com