undue balance deduction

On 3rd july i called vodafone customer care for information regarding one day internet plans.One of the agents told me about 2g plan.So as per his information I activated on 8th july. But my huge amount of balance deducted.I calle dcustomer care,they told me this plan is for night usage only.What the hell,they dint told me earlier..even their message is also not flashing any such thing. I discussed this with the agent..he told me he cant do anything..and disconnected the phone.Many a times i called thereafter but resulting in poor response from them.
Please help me seek out the solution to this problem as soon as possible.thanks.