Deduction of balance from docomo without informing

My account balance has been deducted again and again by the communication company tata docomo.When I call to customer care representative,they reply that any service is activated by you and can't be refunded any amount in balance.Yesterday I recharged my account balance with rs.10.When I see the after sometime ,I found that my balance has deducted again .My number is always used in browsing or other internet use but is never used in mobile phone to call or sms to any one.I really disturbed from these activity.I want my balance should be refunded