Airtel — overbilled for service I did not subscribe to

Address:	Chandigarh, Punjab, 140603
Website:	airtel.in

My phone number [protected] and wife's phone is [protected]. Airtel decided to silently add a service called "boosters" into our bill which costs rs. 300 + tax. After a few months of getting billed this way, i finally called up customer support and was told that this service will be stopped and rs. 300 will be reimbursed from each bill for each month. Come next cycle and i am still getting billed for this service on both numbers. I called them up again and was told that they have no prior record of any communication with me.