Indigo Airlines - Rechedule of flight

I wanted to reschedule my flight from kanpur to mumbai from **th to **th Dec. I went to the payment page to pay the rechedule charges. I clicked on review booking to confirm. The page automatically directed to home page to enter the details again. when i entered the PNR - CTNIUW, it shows that i have cancelled my return flight on **th dec and flight from kanpur to mumbai is rescheduled on **th. I contacted the customer care but they are saying its not posssible and made me wait for more than ** mins to be on hold to talk to a senior executive and still he did not responded. I have a call recording for this. Your app was not working for that time as i wanted to change another ticket and i have a screen recording for that too. Resolve this matter today as I am a school teacher and my students have to participate at an event in mumbai anyhow.