Cheated by charging more amount of bill

i had opted for postpaid from prepaid in vodafone where they had given me door to door service. the plan was of rs 484+taxes i received the bill of rs 1670 where they say that your net usage where around 800rs. i dont feel that i have consumed this much of net and they did not give me proper clarification as well i wanted to shut this no. but they say you have to pay your whole bill…. please help me and let me know what can i do next.