Air India — Denied check in despite mobile boarding pass and being on time

I had an Air India (AI 0024) flight from Delhi to Bombay on 11th Dec, 2016 at 6pm. I reached the airport at 5:10pm and was standing at "Air India All Domestic Flights Check-in counter." However, the check-in was from the international counter and I (along with few other passengers) had to rush to that counter. It was 5:15pm and I asked one officer if this is the right counter and that I might get late. I was told to stand in line. By the time I reached the counter, it was 5:27pm and though web checked in passengers are allowed half an hour prior, they said the counter is closed and that I should speak with the duty officer. The duty officer (Harnimrat Kaur) was not ready to accept that I was on time at the airport and that I wad told to stand in the line. In addition, she tried to blame it all on me and said I was not at the airport. The officer at the counter refused to speak on my behalf that I was at the counter on time. Though I had web checked in and had a mobile boarding pass, they did not allow me. I had to reschedule my flight which cost 14000 with no mistake of mine. Just because it is a governt organisation, doesnt mean they can do anything to increase business!!