Air Asia — ticket fare

Booking number is tt97qe. I booked my tickets today for 18939inr. But today’s rate is 10351 inr. How come fair difference occurs on the same day?? I need the difference amount back. It’s not good to book in a high fair and in some hours the fair drops down. I need to get a solution for the fair difference. I am a regular customer using air asia flights for 2 years