Air India — wrong seat allocation even after pre booking the seat while booking the flight ticket online

What is the point of pre booking the seat for which amount has already been paid and finally while boarding the flight get to see that a different seat has been allocated. Is this what the seat charge was paid!! Paid the amount who will reimburse the same?? Air india. My money is not black money, so i need proper justification about the uneducated staffs which air india are paying who don't even have courtesy to speak with passengers on a proper tone. However, person who generated the ticket never checked that my seat was pre booked for which the amount has been paid from my pocket i want my money back. If proper action is not taken will take stern action. May be this is the reason why airline industry is suffering losses.