Vodafone — Vodafone GPRS Service (Uneccessary balance deduction)

On 19th november morning i found my balance to be RS -104 (negetive 104). When i called the cutomer care (111 from vodafone mobile) they said i had downloaded a game from indiagames which cost me rs.99 . My balance the previous day was rs.2 and after that virtual download of the game it came to -104rs. I assured them i did not download any such game, but they replied that their systems dont lie indirectly stating i m a fool to complain. I requested them to register a complain, so incase there is a mistake from their part it may get cleared. But they refused to take any such complains because their system indicated that i had downloaded a game (and telling me their systems are flawless). Then they agreed to transfer my call to their senior representative, but after transfering the phone just rang for a long time but no reply from the senior. This whole conversation was repeated almost 10 times as i had to call again hoping this time i would get connected to their senior (and i had to repeat all details again because everytime a new representative picked the call ) but again no one picked. I have realised its no use calling them, and they dont agree its their mistake.
Why should i pay for what i havent used?