Vodafone India — Excess bill charged

Address:

208027

My name is anjali sachan. I have a vodafone postpaid connection. Last month they send us excess bill as per my usage. I took the plan of 499 and including service tax the bill should be maximum 550. But the vodafone send me a bill of 1267 rs. When i contact to vodafone care they refuse to correct my bill. And told me that u have to pay all the bill. When i asked about the bill. She told me that u used access 1 gb more data that why they charge 500 rs excess in my bill.
Plese do the needful