Air Asia — Unnecessary charges for blocking the seats

Website:

aisasia.com

My sister and her family was travelling through airasia on date june 26, 2016, with pnr number r8i8nb from bangalore to delhi. When she reached to the counter the counter representative told her she didn't block the seats online so she had to pay rs 200 per seats for getting the seat in the flight, my sister argued about that, the counter representative excused by saying with budget flight you have to pay these kind of the charges as my sister was travelling with one infant and 2 child below 10 years so she was not in that condition to argue much and they charged her rs. 600 for 3 seats, i went through airasia seat policy and such conditions are not mentioned. Is this the way to get extra money from customers. This is the case of cheating and fraud.