HappyEasyGo — excess charges to reschedule an air flight for senior citizen

We booked an air ticket from hyderabad to delhi through happyeasygo online air ticket booking site for air asia for 20th februay 2020 for rs 4704. My mother is 84 years old and is travelling alone. She is returning to delhi from hyderabad after attending her sisters funeral. After few minutes of booking through happyeasy go site we wanted to reschedule the date from 20th feb to 11th february as we found a companion to accompany her for 11th february. We contacted the customer care centre for happyeasygo and the call centre representative said that we will receive an email to inform us of the charges applicable to reschedule the date. We received the email stating that the following charges will be applicable -

Airline rescheduling penalty-rs 2500
Fare difference - rs 1968
Heg service fees - rs 1500
Total penalty - rs 5968

My issue is that i have already paid rs 4704 for flight dated 20th february and the fare for 11th february on the site is around rs 5000. Why is the penalty rs 5968 when the new ticket rs 5000. This means that if i reschedule the flight then i have to pay an extra rs 5968. The total expense is rs 4704+ rs 5968=rs 10672.

I request you to resolve the issue and charge the nominal charges to reschedule.

Secondly, the staff at happyeasygo is vey rude.