Indigo Airlines — Refund of cancelled tickets not justified

I had booked the tickets on 16.4.2015 for mumbai to delhi and back. My PNR No is SCQUSN AND FLIGHT NO 6E-178.Due to some unavoidable reasons i cancelled the tickets on 17.5.2015.I got refund of only 1792.it was credited in my account.Next day i enquired with the toll free no[protected] about the issue they said that i had booked as no refund ticket. Just tell me will somebody will opt for such an option.then i had asked for the breakup of thew recovery but they have not provided.Total paid fare was 6036, refunded by indigo airlines only 1792/- even though i had cancelled the tickets much in advance i.e my onward journey is 1.7.2015 and return jouney is 4.7.2015. The actual cancellation charges are 750 wereas the company has deducted morew than 4000/-. In view of the above facts please refund the balance amount. I had complaint on 15.5.2015 also. It is once requested that the balance amount may please be refunded.