Vodafone - Irrelevant amount added in monthly postpaid mobile bill

I am continuously receiving additional amounts in my Vodafone postpaid bill. These additional amounts are sometimes in the name of VAS, Sona Jeeto contest etc as quoted by Vodafone customer care. I am very confident that I have never subscribed to any special Vas services or have never played any such stupid contest from my phone. I have been communicating the same to Vodafone customer care continuously. But they are rigid that this won't be removed from your bill and you are forced to pay such additional amounts. I am fed up because this has happened thrice till now. I seriously need help here because this has become a pain area for me every month.