Indigo Airlines — missed flight - very bad customer experience

Hi,
This is prashanth & i had booked tickets for 2 adults in indigo airlines to travel from blr-kolkatta-bagdogra (Ixb) on 2nd sep 2017. Just 2 mins before we boarded the flight, we were told that i cannot board the aircraft since i had a power bank in my check-in baggage. I understand that we should not have checked-in powerbank, but i should have atleast been told at the check-in counter if i had a power bank or at least an announcement was made once indigo airlines figured out that there was a powerbank in my check-in baggage. We had cleared our security almost 50 mins before our departure. Indigo airlines could have announced or probably called me to verify my baggage and they did not do this. The lady near the gate mentioned that we cannot board the flight 2 mins before that gate closure. This is not fair at all.
When i requested we can travel in the next flight which is at 08:20 am to kolkatta after our check-in baggage was cleared. But the reservation manager told me that this is not possible at all and we could not cancel our next flight leg (From kolkatta to bhadogra). When i escalated this issue to the one of the mananger, he asked us pay additional amount of rs 3200/ticket (Ie 6400 rs for 2 people) for us to travel to kolkatta after we paid the amount, we see that there was about 10 seats which was vacant
Indigo airlines could have handled the situation much better and this left us in a very bitter experience overall.

Flight no: 6e-339
Time: 06:20

Regards
Prashanth
Mobile no: [protected]