I was once charged incorrectly by air India for an award ticket at the time of check In when clearly I was not supposed to be. The only way left for me to travel was to pay up then. I did and upon landing in Bombay I wrote a letter and submitted it to the air India building in nariman point. Within a month my refund check had been posted to me.

However, I was clearly in the right then. You could try doing this with air India.