netflix - Money debited from debit card without permission

Hi,
I had registered on netflix and paid for ***rs plan. Had made the payment through my Debit card, post one month they changed my plan automatically to ***rs and charged directly from my bank account. I called customer care and she was least bothered. she told me u cancel the plan now and we dont charge you next month. when i told her i had not changed the plan since i watch on phone and tablets, she said someone else might have changed. i asked her to send proof if that was the case, but they dint have any sort of proof.

I am very upset with them. i want my money return and why should i pay for something that i have used the service.