Airtel Mobile
Not getting bill statement

I am not getting my mobile bill of airtel from past 6 months earlier i was getting all information and i could pay my bill on internet account provided at their website but from 2 months my id has been deactivated and after repeated contacting on 121 help line they always said that their system is getting upgrade and never responded and this month they overcharged me and moreover not providing any details.

kindly suggest they way forward.