Indian Railway Catering & Tourism Corporation [IRCTC] — Train cancelled and got partial refund

I booked a ticket from Nagpur to Pune in Garibrath Express for 4th of December, however the train got cancelled and we were informed only about 2 weeks before and all other trains were already waitlisted.
Today I received a refund for the same but the amount I received is ₹870.28 while we paid ₹893.95, the difference is of convenience fees which IRCTC ask us to pay while booking, but since it is IRCTC who cancelled the train itself we want that convenience charge back as well.