Airtel — inappropriate charging of bill amount

I'm on international roaming since july'17 and i confirmed with airtel customer care if i should convert my number to prepaid from postpaid to avoid overcharging of bills. Following are my issues:
1. Team misinformed me that i will get a bill of only rs 149 per month for using postpaid number, with which i will be able to receive sms and number will remain active. And no surprise, i received a bill of around inr 6000.
2. Team continuously ignored my emails knowing that i cannot reach them physically. On asking senior management's contact details, no response was given. When my fiancée reached out to them, they reduced the bill amount on their own to 1800, which is still too much as compared to what i was supposed to pay
3. My number has been deactivated and i am always a international tollfree number. Is it not common sense that if you deactivate someone's number, they can't call you back
4. When i gave my international number to contact me, nobody reached out to me
5. Even when this dispute is on, airtel is charging late payment fee charges to me. Are you kidding me, i am not even using your service and still i am liable to pay these charges??
I have a count of 59 emails exchanged between the team and myself in last 1 month and this is my last try to post it here. I would reach out to regulation authority if you guys still don't resolve this issue.