Spice Jet Airlines — for refusing boarding

Hello, i m anil vaghasia. I had a flight from goa to ahmedabad on 20 oct 2017 on 5:00 pm. We arrived at boarding counter on 4:35.. At that time spice jet said that we cant let u board for flight coz time is over.. U hav to get another flight. On boarding pass we read that we should reach at boarding counter prior to 20 mins for domestic flight. And then they asked for next flight to ahmedabad at 5:55pm on 7071/- inr per person and they board us on 5:12 pm.. We purchased 5 tickets at 35335/- inr. Though its boarding overed they boarded us. And before that we reached before time they refused on our earlier flight. Isnt it unjustice with us? We know only that we reached 4:35 and that was before 20 mins for 5:00..