Videopindw activated without my consent and money deducted

My Airtel number 9008463345 was having a self activation of a service called VIDEOPINDW without my knowledge. I hardly use this number, hence had kept a small balance amount for urgent calls. And this stupid service says activated when I have not used it and deducted 15₹. Calling customer care was of no help, they just deactivated it... I want my refund as soon as possible.. how can Airtel cheat their customers this way?? I need a response!