Indigo Airlines — Unreasonable rules and cancellation charge

Address:	Gurgaon, Haryana, 380054
Website:	www.goindigo.in

My booking reference number is j895gc. The ticket is booked for 4 persons from lucknow to ahmedabad. One of the person wants to change his travel date from 25th jan'17 to 26th jan'17. I had booked all the tickets from the airport counter. When i went there to postpone it by a day. I was sent back saying that the cancellation can only be done online. Thats a rule. What kind of rule is this?
Are you there to facilitate your customers or make them suffer?
I have mailed 2 days back on the indigo website also, asking them to guide me, but, no reply from there too.
Why such a lethargic behaviour. Your airline is supposed to be a very professional corporate one. But, it seems i am being proved wrong.
Another matter is why am i being charged 2250/- for cancellation? I only want to postpone by a day, not cancel my ticket. What kind of rule is this? Whay am i being charged such an exaggerated amount?