no service received, but received a bill for the same

Location/place: balngalore

Name of company/service: tata docomo

on 23rd april 2013 We got a broadband connection installed and was told that its a wifi connection and hence had to pay 1000RS for the device, on the day on installation we were told that it cant be a wifi connection as the system that they have in our building do not support the wifi, however we went ahead with the wire connection. he installed it and showed it to us on a laptop but after that day the connection is not working. i raised a complaint calling the customer care on 1st may 2013 but i still havent received any resolution and hence i am unable to use the internet. but i get a bill for the same on 10th of may 2013 for 500rs i have never used the internet from the day we got it installed but we get a bill for something we have never used.