wrong deduction of balance

Last 31 may night at 11.50 pm. Suddenly Rs. 170 deducted from my Airtel Prepaid Number is 9957019545. Within a minute I called the customer care number and told my complaint why deducted my balance. They replied me that that time nothing showing on their data so they take my complaint as register no. CBDCC30601000213 and they committed that my complain would be solve in 11am on 2nd June.
Today I called again customer care about 1pm and ask them with complain registered no. After half n hour conversation they can’t be able to give me the reason of deduction of my balance. They said me that may be download something or click charge site . as for their information I have many times told them I have 20 MB 3G data balance remain in my data account and I am very sure I wnt dow ndodnnlo