Tata docomo 3g data is been deducted

I had activated a 3g pack of 246 rupees...which promised to give me 1gb 3g data for 30 days...after 10 days I had used 400 mb data...and with out notice the network provider (tata docomo) have deducted my 3g data to 7 mb and reduced my balance by 4 rupees... enquiring about the same with the customer care...I dint get proper response and when I turned up to their tata docomo store...they said u have used up all the data and dint take complaint regarding the same... please help with this... thanking you...