Vodafone India — My Balance got deducted automatically

Address:

Hyderabad, Andhra Pradesh

On 06/30/2015 my vodafone balance rs 120.00 got deducted automatically. They are saying that i have used internet. This what has happened.
1. My internet on
2. I have sent a message to 199 "data bal" and i got response saying you have balance of 0.01 mb at time 11.59.59 pm after 30 seconds i have turned off my internet connection and i got a message saying your balance is reduced due to internet usage of 29 mb . My question is how can i use 29 mb in 30 seconds. Plz adjust my balance