Reliance Communications — Extra amount added in bill

Address:

Thane, Maharashtra, 421004

I had pending bills for two months visited the reliance communication for the bill payment and closing account request at ulhasnagar.They made me to talk with customer care people stating that do not pay now and give the closing request only. Once the number will close you will get a call and pay after that.
So I gave the closing request. They took almost 15 days to process it and generated a new bill in between.
When I was paying full bill and trying to close my account they did not allow me in return made me to wait ad added almsot 400 extra in my outstanding bill.
Also when I ask for explanations the customer representative said me if you do not pay this much now I will put you in defaulter and you will not get any loan in future.
Kindly help addressing this issue.