MakeMyTrip India — Pnr ontr4k reschedule

I reschedule in dig flight from june 16 to august 25the due to high covid pandemicnand lockdown in chennai. I got a mil from indigo that there is refund of 4150 but make my trip is denying to refund it. Now when i am rescheduling back to july, they are charging 3200 stating there is difference in price. When price reduces they will not refund but when price is more they charge. This is not fare. I will have to complain to ombudsman and rti in this case