INDIGO - Ticket got cancelled without intimation

We had initiated flight reschedule for *th March instead of *th March by calling the customer care around mid February ****. An email was shared to pay the difference of ***** Rs for rescheduling the flight. But as the amount was too high we decided not to proceed with re-scheduling and assumed it would be cancelled automatically and we will travel on original date which is *th March ****. On arriving at airport on *th we were denied boarding the flight stating that we had rescheduled the flight and status was payment pending. We didn't receive any communication regarding the payment pending status between the call and day of travel. We had assumed the rescheduling would be cancelled automatically as payment was never done similar to how you do online through web or mobile app. We were a bit surprised upon reaching the airport and requested to board the flight but were not allowed. This caused us a lot of stress. We were compelled to book a new indigo flight on the spot costing us ***** Rs (PNR: R*BH*K)