False bill

Location/place: Bangalore

Name of company/service: Tata Docomo Postpaid Mobile Connection

I have subscribed to tha plan of Rs 899 unlimited local and STD calls plan last month. Along with that I even activated a message and 3G data usage plan.On 15/7/13, I got a message that my bill amount is Rs 6401.47 and my outgoing calls will be barred till I pay the bill. How can I get a bill of Rs 6000+ when I already have taken Rs 899 unlimited plan? In case of exceeding any data usage, a warning message comes from customer care. I DID NOT RECEIVED ANY WARNING MESSAGE.The customer care is not responding and reverting in this matter. They are not even activating my outgoing facilities. And are asking me to pay a min amount of Rs. 4000. This is totally illegal.