All airline companies are cheating us with cancellation and reschedule charges even when we do it way in advance. 
I had flight booked with Indigo and had an important meeting because of which I needed to change it. I requested them a hell lot that I just need the next flight after my current one. Yet they said the process says I needed to pay additional 3k amount for it. A ticket that cost 9.5k. Taking more than 30% as rescheduling charges is just not fair. 
This is pure penalisation for no mistake of ours. 
extremely one sided rules set by airplanes.