Wrong charges to my mobile bill

I had switched to post paid tata docomo connection in the month of May 2014. My mobile no is 9730364105. Soon after, I moved to Singapore and subscribed to international roaming by paying the deposit of 3000 rupees. But as I moved to Singapore, I started getting email alerts that my usage is very high and I should monitor it. I was surprised as I did not make any outgoing calls neither did I get any incoming calls. Therefore I called customer care using 121 dialing and asked where the usage is coming from. The representative told me that they cannot inform as the bill is not generated. I then asked if the charges are for 121 calling while in roaming. I was again told that there are no charges for 121 calling while in international roaming. But, I continued to get alerts for high usage. I called again to 121 # and double confirmed that there is no charge of 121 and I was again told the same. But, towards the end of month, I received a huge bill of 7769 rupees. I asked customer care to revise the bill and take out charges for 121 calling. But, I was told that the charges are correct and I must pay the entire amount to restore my service. I challenged Tata Docomo to verify the call records about incorrect information given by their representative. But, they told me that all the charges are correct. Now I feel harassed as I am charged for no fault of mine. Moreover, I cannot received my phone banking alerts as my service is discontinued. I need help to get my service restored and waive of my charges.