Airtel Mumbai — Over Billing

My phone number is [protected] in the name of my company Mahaveer Impex.

I wanted to use GPRS service on my phone so I called Airtel 121 services there one Customer Service Executive said I can get GPRS service (Airtel Office) @ 199 with unlimited use. He also said that there will no other charges for it so I ask him to activate this service. but when I get the bill of previous month Airtel charged 1498/- for GPRS service. I called again 121 but they said they had not activated Airtel Office @ 199 Rs.

I want to take legel action for this.